Enhanced Catalytic Reactions in a Coking Process to Improve Process Operation and Economics

ABSTRACT

Heavy gas oil components, coking process recycle, and heavier hydrocarbons in the delayed coking process are cracked in the coking vessel by injecting a catalytic additive into the vapors above the gas/liquid-solid interface in the coke drum during the coking cycle. The additive may comprise cracking catalyst(s) and quenching agent(s), alone or in combination with seeding agent(s), excess reactant(s), carrier fluid(s), or any combination thereof to modify reaction kinetics to preferentially crack these components. The quenching effect of the additive may be effectively used to condense the highest boiling point compounds of the traditional recycle onto the catalyst(s), thereby focusing the catalyst exposure to these target reactants. Exemplary embodiments of the present invention may also provide systems and methods to (1) reduce coke production, (2) reduce fuel gas production, and (3) increase liquids production.

This application claims the benefit of U.S. Provisional Application No.61/794,192, filed Mar. 15, 2013, which is hereby incorporated byreference in its entirety. This application is also acontinuation-in-part of Ser. No. 13/765,461, filed Feb. 12, 2013, whichis a continuation of U.S. application Ser. No. 12/371,909, filed Feb.16, 2009, now U.S. Pat. No. 8,372,264, which is a continuation-in-partof Ser. No. 12/377,188, filed Feb. 11, 2009, now U.S. Pat. No.8,372,265, which claims priority to PCT Application No.PCT/US2007/085111, filed Nov. 19, 2007, which claims priority to U.S.Provisional Application No. 60/866,345, filed Nov. 17, 2006, each ofwhich is hereby incorporated by reference in its entirety.

BACKGROUND AND SUMMARY OF THE INVENTION

Exemplary embodiments of the invention relate generally to the field ofthermal coking processes, and more specifically to modifications ofpetroleum refining thermal coking processes to selectively and/orcatalytically crack or coke components of the coker feed, recycle, andgas oil process streams and increase production of more valuable productstreams. Exemplary embodiments of the invention also relate generally tothe production of various types of petroleum coke with uniquecharacteristics for fuel, anode, electrode, or other specialty carbonproducts and markets.

Thermal coking processes have been developed since the 1930s to helpcrude oil refineries process the “bottom of the barrel.” In general,modern thermal coking processes employ high-severity, thermaldecomposition (or “cracking”) to maximize the conversion of very heavy,low-value residuum feeds to lower boiling hydrocarbon products of highervalue. Feedstocks for these coking processes normally consist ofrefinery process streams which cannot economically be further distilled,catalytically cracked, or otherwise processed to make fuel-grade blendstreams. Typically, these materials are not suitable for catalyticoperations because of catalyst fouling and/or deactivation by ash andmetals. Common coking feedstocks include atmospheric distillationresiduum, vacuum distillation residuum, catalytic cracker residual oils,hydrocracker residual oils, and residual oils from other refinery units.

There are three major types of modern coking processes currently used incrude oil refineries (and upgrading facilities) to convert the heavycrude oil fractions (or bitumen from shale oil or tar sands) intolighter hydrocarbons and petroleum coke: delayed coking, fluid coking,and flexicoking. These thermal coking processes are familiar to thoseskilled in the art. In all three of these coking processes, thepetroleum coke is considered a by-product that is tolerated in theinterest of more complete conversion of refinery residues to lighterhydrocarbon compounds, referred to as ‘cracked liquids’ throughout thisdiscussion. These cracked liquids range from pentanes to complexhydrocarbons with boiling ranges typically between 350 and 950 degreesF. In all three of these coking processes, the ‘cracked liquids’ andother products move from the coking vessel to the fractionator in vaporform. The heavier cracked liquids (e.g. gas oils) are commonly used asfeedstocks for further refinery processing (e.g. Fluid CatalyticCracking Units or FCCUs) that transforms them into transportation fuelblend stocks.

Crude oil refineries have regularly increased the use of heavier crudesin their crude blends due to greater availability and lower costs. Theseheavier crudes have a greater proportion of the ‘bottom of the barrel’components, increasing the need for coker capacity. Thus, the cokeroften becomes the bottleneck of the refinery that limits refinerythroughput. Also, these heavier crudes often contain higherconcentrations of large, aromatic structures (e.g. asphaltenes andresins) that contain greater concentrations of sulfur, nitrogen, andheavy metals, such as vanadium and nickel. As a result, the cokingreactions (or mechanisms) are substantially different and tend toproduce a denser, shot (vs. sponge) coke crystalline structure (ormorphology) with higher concentrations of undesirable contaminants inthe pet coke and coker gas oils. Consequently, these three cokingprocesses have evolved through the years with many improvements in theirrespective technologies.

Many refineries have relied on technology improvements to alleviate thecoker bottleneck. Some refineries have modified their vacuum crudetowers to maximize the production of vacuum gas oil (e.g. <1050 degreesF.) per barrel of crude to reduce the feed (e.g. vacuum reduced crude orVRC) to the coking process and alleviate coker capacity issues. However,this is not generally sufficient and improvements in coker processtechnologies are often more effective. In delayed coking, technologyimprovements have focused on reducing cycle times, recycle rates, and/ordrum pressure with or without increases in heater outlet temperatures toreduce coke production and increase coker capacity. Similar technologyimprovements have occurred in the other coking processes, as well.

In addition, coker feedstocks are often modified to alleviate safetyissues associated with shot coke production or ‘hot spots’ or steam‘blowouts’ in cutting coke out of the coking vessel. In many cases,decanted slurry oil, heavy cycle oil, and/or light cycle oil from theFCCU are added to the coker feed to increase sponge coke morphology(i.e., reduce shot coke production). This increase in sponge coke isusually sufficient to alleviate the safety problems associated with shotcoke (e.g. roll out of drum, plugged drain pipes, etc.). Also, theincrease in sponge coke may provide sufficient porosity to allow bettercooling efficiency of the quench to avoid ‘hot spots’ and steam‘blowouts’ due to local areas of coke that are not cooled sufficientlybefore coke cutting. However, the addition of these materials to cokerfeed reduces coking process capacities. Alternatively, many refinerieslimit the use of crudes in their refinery crude slate that causecomponents in the coker feed that neither crack or coke in thetraditional coking process and cause ‘hot spots’ and/or steam ‘blowouts’due to insufficient cooling of these hot liquids at the end of thecoking cycle.

Unfortunately, many of these technology improvements have substantiallydecreased the quality of the resulting pet coke. Most of the technologyimprovements and heavier, sour crudes tend to push the pet coke fromporous ‘sponge’ coke to ‘shot’ coke (both are terms of the art) withhigher concentrations of undesirable impurities: Sulfur, nitrogen,vanadium, nickel, and iron. In some refineries, the shift in cokequality may require a major change in coke markets (e.g. anode to fuelgrade) and dramatically decrease coke value. In other refineries, thechanges in technology and associated feed changes have decreased thequality of the fuel grade coke with lower volatile matter (VM), grossheating value (GHV), and Hardgrove Grindability Index (GHI). All ofthese factors have made the fuel grade coke less desirable in the UnitedStates, and much of this fuel grade coke is shipped overseas, even witha coal-fired utility boiler on adjacent property. In this manner, thecoke value is further decreased.

More importantly, many of these coker technology improvements havesubstantially reduced the quality of the gas oils that are furtherprocessed in downstream catalytic cracking units. That is, the heaviestor highest boiling components of the coker gas oils (often referred toas the ‘heavy tail’ in the art) are greatly increased in many of theserefineries (particularly with heavier, sour crudes). In turn, theseincreased ‘heavy tail’ components cause significant reductions in theefficiencies of downstream catalytic cracking units. In many cases,these ‘heavy tail’ components contain polycyclic aromatic hydrocarbons(or PAHs) that have a high propensity to coke and contain much of theremaining, undesirable contaminants of sulfur, nitrogen, and metals. Indownstream catalytic cracking units (e.g. FCCUs), these undesirablecontaminants of the ‘heavy tail’ components may significantly increasecontaminants in downstream product pools, consume capacities of refineryammonia recovery/sulfur plants, and increase emissions of sulfur oxidesand nitrous oxides from the FCCU regenerator. In addition, theseproblematic ‘heavy tail’ components of coker gas oils may significantlydeactivate cracking catalysts by increasing coke on catalyst, poisoningof catalysts, and/or blockage or occupation of active catalyst sites.Also, the increase in coke on catalyst may require a more severeregeneration, leading to suboptimal heat balance and catalystregeneration. Furthermore, the higher severity catalyst regenerationoften increases FCCU catalyst attrition, leading to higher catalystmake-up rates, and higher particulate emissions from the FCCU. As aresult, not all coker gas oil is created equal. In the past, refineryprofit maximization computer models (e.g. Linear Programming Models) inmany refineries assumed the same value for gas oil, regardless ofquality. This tended to maximize gas oil production in the cokers, eventhough it caused problems and decreased efficiencies in downstreamcatalytic cracking units. Some refineries are starting to put vectors intheir models to properly devalue these gas oils that reduce theperformance of downstream process units.

In addition, prior art of the coking process has been dedicated totechnologies that improve the economics of the coking process,particularly improvements in the product yields (i.e. higher values). Inthis regard, crude oil companies have attempted to introduce catalystsin the coker feed to increase distillate yield and reduce cokeproduction in the delayed coking process.

U.S. Pat. No. 4,394,250 describes a delayed coking process in whichsmall amounts of cracking catalyst and hydrogen are added to thehydrocarbon feedstock before it is charged to the coking drum toincrease distillate yield and reduce coke make. The catalyst settles outin the coke and does not affect the utility of the coke.

U.S. Pat. No. 4,358,366 describes a delayed coking process in whichsmall amounts of hydrogen and a hydrogen transfer catalyst, ahydrogenation catalyst, and/or a hydrocracking catalyst are added to acoker feed consisting of shale oil material and a petroleum residuum toenhance yields of liquid product.

This known prior art adds catalyst to the coker feed, which has chemicaland physical characteristics that create challenging problems anddisadvantages. The coker feed of the known art is typically comprised ofvery heavy aromatics (e.g. asphaltenes, resins, etc.) that havetheoretical boiling points greater than 1050° F. As such, the primaryreactants exposed to the catalysts of the known art are heavy aromaticswith a much higher propensity to coke (vs. crack), particularly with theexposure to high vanadium and nickel content in the coker feed.Furthermore, mineral matter in the coker feed tends to act as a seedingagent that further promotes coking. Calcium, sodium, and ironcompounds/particles in the coker feed have been known to increasecoking, particularly in the coker feed heater. From a physicalperspective, the primary reactants of the known art are a very viscousliquid (some parts semi-solid) at the inlet to the coker feed heater.Throughout the heater and into the coke drums the feed becomes primarilyhot liquid, solids (from feed minerals and coking), and vapors (fromcoker feed cracking and vaporization of some coker feed components). Thetemperature of the multi-phase material at the inlet to the coke drum istypically between 900 and 950 degrees Fahrenheit. Consequently, thecatalyst particles in the coker feed of the known art are exposed to asevere coking environment with coker feed components that have a highpropensity to coke. Since the catalyst tends to act as a seeding agent,the catalyst of the known art would likely be surrounded by coke beforeit has an opportunity to perform its intended purpose to promotecracking of coker feed materials. In commercial applications of theknown art (i.e. catalyst in the delayed coker feed), excessive cokingproblems have been noted. The known art attempts to have the catalystgenerally address all of the coker feed as its target reactants. Many ofthese chemical compound (e.g. coker feed components) have a highpropensity to coke or readily crack in the traditional thermalenvironment of the delayed coking process. However, a more prudentapproach may be to focus the use of catalyst in the liquid and foamlayers, where coker feed components and cracked intermediates havedifficulty either cracking or coking in the traditional thermalenvironment of the delayed coking process. As such, an active catalystwith proper characteristics can be more effective in these reactionzones, but getting active catalyst to these moving layers in anefficient and cost effective manner is very challenging. Injectingcatalyst from the bottom apparently doesn't work. Injecting activecatalyst from above of the foam/liquid layers has its own challenges, aswell. Injecting catalyst alone form the top of the drum would likelycreate substantial vapor overcracking with much greater production oflow value fuel gas due to direct exposure of cracking catalyst to theproduct vapors. Initially, the Applicant developed an option using amodified drill stem that would inject an active catalytic additive intothe foam/liquid layers from close proximity (e.g. within 5-10 feet) byleading these rising layers up the coke drum. However, this approachbecame somewhat cumbersome and costly with significant safety concernsassociated with consistent sealing the modified drill stem with highcoke drum operating pressures (e.g. >15 psig).

It has been discovered that a more efficient approach is to use carrierfluid(s) and/or quench agent(s) with the catalyst to take advantage ofthe condensation of traditional recycle components to limit exposure ofcatalyst(s) to the product vapors and protect its activity until itreaches the foam/liquid layers. An added benefit is the potentialcracking of these traditional recycle materials to favorably change thereaction equilibriums to offset the reduction in liquid yieldsassociated with lower coke drum outlet temperatures. In addition, thequench also provides added benefits of reducing external recycle, whileterminating vapor overcracking reactions and reducing the production oflow value fuel gas.

In contrast, an exemplary embodiment of a catalyst of the presentinvention may only be exposed to target reactants downstream of theprimary coking zone of the coking process, which has substantiallydifferent chemical and physical characteristics than the targetreactants of the known art. These target reactants include coker feedcomponents (or cracked intermediate hydrocarbons) in the liquid layerabove the coke that have difficulty cracking or coking in the thermaloperating environment of the traditional coking process. In an exemplaryembodiment of the present invention, a catalytic additive reduces theactivation energy required to crack (preferably) or coke these cokerfeed components (or cracked intermediate hydrocarbons). In this manner,the catalyst reduces the amount of heat needed for similar endothermiccracking (preferably) and/or coking reactions (i.e. same reactants andsame products) and promotes cracking (preferably) and/or cokingreactions for coker feed components (or cracked intermediatehydrocarbons) that have difficulty cracking or coking in the thermaloperating environment of the traditional coking process.

In the present invention, a catalytic additive is introduced into thecoking process in a manner differentiated over the known art thatreduces coke production and increases the yields of ‘cracked liquids,’while addressing problems noted above and improving operations andmaintenance of the coking process. Though examples of the presentinvention may primarily address issues of the delayed coking process,some utility and advantages of exemplary embodiments of the presentinvention may also be applied to the fluid coking and flexicokingprocesses.

Accordingly, exemplary embodiments of the present invention may improveproduct yields, operations, and maintenance of a coking process, whilealleviating problematic operational and product issues. Exemplaryembodiments are described herein, which may address or provide examplesof (1) the benefits of introducing effective catalyst(s) into theprimary reaction zones of a delayed coking process, (2) the primaryadvantages of exemplary embodiments of the present invention, and (3)the broad coverage of the intellectual property associated with theexemplary embodiments. U.S. Publication No. 2006/0032788 is incorporatedherein by reference in its entirety.

One exemplary embodiment of the present invention may improve productyields of a coking process: (1) Reduce coke production, (2) Increase‘cracked liquids’ (e.g. distillates), (3) Increase high-value gases(e.g. BBs and PPs), and/or (4) Decrease low-value fuel gas.

One exemplary embodiment of the present invention may provide control ofthe amounts of problematic components in the coker recycle to the cokerheater and/or ‘heavy tail’ components going to the fractionators ofthese coking processes and into the resulting gas oils of the cokingprocesses, while maintaining high coker process capacities. By doing so,an exemplary embodiment of the present invention may significantlyreduce catalyst deactivation in downstream catalytic units (cracking,hydrotreating, and otherwise) by significantly reducing coke on catalystand the presence of contaminants that poison or otherwise block oroccupy catalyst reaction sites. An exemplary embodiment of the presentinvention may more effectively use the recycle and/or gas oil ‘heavytail’ components by (1) selective catalytic cracking them to increase‘cracked liquids’ yields and/or (2) selective catalytic coking of themin a manner that improves the quality of the pet coke for anode,electrode, fuel, or specialty carbon markets. In addition, an exemplaryembodiment of the present invention may reduce excess cracking ofhydrocarbon vapors (commonly referred to as ‘vapor overcracking’ in theart) by quenching such cracking reactions, that convert valuable‘cracked liquids’ to less valuable gases (butanes and lower) that aretypically used as fuel (e.g. refinery fuel gas).

One exemplary embodiment of the present invention selectively cracks orcokes the highest boiling hydrocarbons in the product vapors to reducecoking and other problems in the coker and downstream units. Anexemplary embodiment of the present invention may also reduce vaporovercracking in the coker product vapors. Both of these properties of anexemplary embodiment of the present invention may lead to improvedyields, quality, and value of the coker products.

In addition, an exemplary embodiment of the present invention mayprovide a superior means to increase coking process capacity withoutsacrificing coker gas oil quality. In fact, an exemplary embodiment ofthe present invention may improve gas oil quality, the quality of thepetroleum coke, and/or the quality of downstream products, whileincreasing coker capacity. The increase in coking capacity also leads toan increase in refinery throughput capacity in refineries where thecoking process is the refinery bottleneck.

An exemplary embodiment of the present invention may increase spongecoke morphology to avoid safety issues with shot coke production and‘hot spots’ and steam ‘blowouts’ during coke cutting. In many cases,this may be done without using valuable capacity to add slurry oil orother additives to the coker feed to achieve these advantages. Anotherexemplary embodiment of the present invention may catalytically crackand/or catalytically coke components in the coker feed that neithercrack or coke in the traditional coking process and avoid ‘hot spots’and/or steam ‘blowouts’ due to inefficient cooling of these hot liquidsat the end of the coking cycle

In addition, an exemplary embodiment of the present invention may alsobe used to enhance the quality of the petroleum coke by selectivecatalytic coking of the highest boiling hydrocarbons in the coke productvapors to coke with preferred quantities and qualities of the volatilecombustible materials (VCMs) contained therein.

An exemplary embodiment of the present invention may also allow crudeslate flexibility for refineries that want to increase the proportion ofheavy, sour crudes without sacrificing coke quality, particularly withrefineries that currently produce anode grade coke. Furthermore, anexemplary embodiment of the present invention may reduce shot coke in amanner that may improve coke quality sufficiently to allow sales in theanode coke market.

Finally, an exemplary embodiment of the present invention may provide asuperior means to improve the coking process performance, operation, andmaintenance, as well as the performance, operation, and maintenance ofdownstream catalytic processing units.

All of these factors potentially improve the overall refineryprofitability. Further utility and advantages of this invention willbecome apparent from consideration of the drawings and ensuingdescriptions.

In view of the foregoing, an exemplary embodiment of the presentinvention may be an improvement of coking processes that adds anadditive to the coking vessel of a coking process to convert (e.g. viacatalytic cracking) intermediate, heavy hydrocarbon species (i.e.created by thermal cracking of coker feed) of the coking process toimprove the quality and/or value of the products of the coking process.The basic technology contemplated in U.S. Provisional Application No.60/866,345 uses this additive (often containing catalyst) to crack orcoke high boiling point compounds in the coking vessel of a cokingprocess. As indicated, ‘conversion includes cracking these high boilingpoint compounds to lighter hydrocarbons,’ including ‘naphtha, gas oil,gasoline, kerosene, jet fuel, diesel fuel, & heating oil.’ In U.S.application Ser. No. 12/377,188, various other exemplary embodiments arediscussed, including the use of the additive (with or without catalyst)as a quenching agent to reduce vapor overcracking reactions. Muchdiscussion is devoted to what is considered one of the best modes ofoperation for the present invention, which uses the additive (withcatalyst) to selectively convert (preferably cracking) the highestboiling point materials in the product vapors of the coking process tominimize the coker recycle and/or significantly improve the quality ofthe heavy coker gas oil. By converting these problematic components tolighter liquid products and/or higher quality petroleum coke, thisexemplary embodiment of the present invention potentially provides thegreatest upgrade in value for the coking process: (1) increasing liquidyields, while decreasing coke yields, (2) minimizing coker recycle bycreating an ‘internal recycle,’ (3) improving quality of coker gas oiland/or petroleum coke, (3) reducing ‘vapor overcracking’ and associatedloss of liquids to lower value gases, (4) reducing totspots' and/or‘blowouts’ & associated safety issues and costs, (5) increasing cokercapacity and potentially refinery capacity, (6) increasing crude slateflexibility, and/or (7) improving operation & maintenance of the cokingprocess and downstream processing units.

In this application, further information is provided to helpdifferentiate the present invention over known art, includingcomparative data from pilot plant tests. In these pilot plant tests, theinjection of the catalyst additive into the coking vessel of the currentinvention and the addition of catalyst to the coker feed of the knownart were compared to a common baseline with no catalyst. In two sets oftest data, the catalyst addition of the known art showed a substantialincrease in coking and a significant reduction in liquid yields. Incontrast, the injection of the catalytic additive of the presentinvention showed a substantial reduction in coke yield and a significantincrease in liquids production. Thus, these tests clearly demonstratedifferentiation of the present invention over the known art. Theseresults are likely due to the major differences in the chemical andphysical nature of the primary reactants, exposed to the catalyst in theknown art versus the current invention. That is, the catalyst in thecoker feed of the known art is exposed to coker feed components thathave a high propensity to coke. In contrast, the catalyst of the presentinvention is only exposed to target reactants downstream of the primarycoking zone. These target reactants include coker feed components (orcracked intermediate hydrocarbons) in the liquid layer above the cokethat have difficulty cracking or coking in the thermal operatingenvironment of the traditional coking process. In an exemplaryembodiment of the present invention, a catalytic additive reduces theactivation energy required to crack (preferably) or coke these cokerfeed components (or cracked intermediate hydrocarbons). In this manner,the catalyst reduces the amount of heat needed for similar endothermiccracking (preferably) and/or coking reactions (i.e. same reactants andsame products) and promotes cracking (preferably) and/or cokingreactions for coker feed components (or cracked intermediatehydrocarbons) that have difficulty cracking or coking in the thermaloperating environment of the traditional coking process. Furtheranalyses are provided in this regard. Finally, an improvement to thepresent invention is claimed relative to the use of the quenching effectof the additive to condense the highest boiling point compounds onto thecatalyst(s), thereby improving the catalyst selectivity. That is, theadditive can focus the catalysts exposure to the highest boiling pointcompounds in the product vapors. With a properly designed catalyst tocrack these highest boiling point materials, this mechanism caneffectively increase the catalyst's selectivity, thereby increasing itsefficiency and reducing catalyst requirements and costs.

An exemplary embodiment of the present invention is a coker processtechnology that effectively introduces a low-cost catalyst(s) in amanner that improves production of valuable transportation fuels andproduct gases, while reducing low-value fuel gas and petroleum cokeby-products. In many cases, the present invention can also help resolvecertain problems with the operation and maintenance of traditional,refinery coker process units. In some cases, the present invention canincrease the coker capacity by effectively debottlenecking cokersections without major capital costs. The remainder of this introductionwill describe the impact of the catalyst and its unique injection on thedelayed coking process, including thermodynamic and reaction kineticperspectives. As discussed below, the presence of a catalyst from thepresent invention in the delayed coking process can favorably change thechemical reaction mechanisms, the coke drum temperature profile, and thevapor-liquid equilibriums in the coke drum during the coking cycle ofthe traditional delayed coking process.

The operational principles of the present invention, as well astechnical and economic viability, have been proven in pilot plant tests,designed to demonstrate, improve, and optimize the Technology. Thesepilot plant tests showed substantial reductions of coke (6-12+wt. %) andfuel gas (up to 15 wt. %). In many tests, these reductions translatedprimarily into increases in gas oil and naphtha production with someincreases in higher value gases (e.g. PPs and BBs with higher olefincontent).

One of the key features of the present invention is the unique injectionof the active catalyst(s) to achieve its desired benefits. In the past,catalyst has been introduced into the coking process through addition tothe coker feed. Apparently, the catalyst was not effective for crackingthe heaviest components of the coker feed (that have a very highpropensity to coke) and the catalyst particles acted as seeding agentsand caused more coke production, rather than less. In contrast, theexemplary embodiments of the present invention have several injectionoptions, but introduce the active catalyst above the rising coke levelin reaction zones, where the catalyst can be more effective. Thepreferred arrangement injects the active catalyst with a carrier oilthat maintains catalyst activity and acts as partial quench thatcondenses traditional recycle components onto the catalyst, creatingintimate contact for desired cracking reactions.

First and foremost, a properly designed catalyst lowers activationenergies for both cracking and coking reactions in the coke drum duringthe coking cycle. With an exemplary embodiment of the present invention,catalysts can preferentially lower cracking reaction activation energiesby up to one third in repetitive reactions in both the vapor and liquidphases of the coke drum. With the long residence time of the cokingcycle (up to hours), each catalyst particle can conceivably reduce theactivation energy for many repetitive cracking reactions in the vaporand preferably in the liquid phase, until the catalyst particleparticipates in enough coking reactions to consume it in the coke. Inthe preferred injection option, the an exemplary embodiment of thepresent invention also quenches excessive cracking of the vapor products(i.e. vapor overcracking) while condensing the heaviest recyclecomponents onto the catalyst, creating an internal recycle and intimatecontact with the catalyst to provide more selective use of the catalyst.Since these recycle components are catalytically cracked to smallerhydrocarbon molecules with higher vapor pressures, most of thesetraditional recycle components exit the coke drum even at lower drumoutlet temperatures.

In many cases, the catalyst of an exemplary embodiment of the presentinvention will also lower the activation energy for coking reactions inan advantageous manner. For example, certain heavy hydrocarbons in somecoker feeds are resistant to cracking or coking in the strictly thermalreactions environment of the traditional delayed coking process. As thecoking cycle proceeds, these materials tend to increase in concentrationand pool in the liquid layer on top of the coke. At the end of thecoking cycle much of this material has neither cracked or coked, and hasbeen noted to cause problems with dangerous ‘hot spots’ in the decokingcycle. Since these heavy hydrocarbons tend to have a much greaterpropensity to coke (vs. crack), the catalyst of an exemplary embodimentof the present invention (designed to preferentially crack) would alsoreduce the activation energy for coking reactions, resulting in thecoking of these materials, and mitigating ‘hot spot’ issues. Inaddition, coking these materials also has the advantage of substantiallyreducing the concentration of these materials in the liquid layer,improving the reaction equilibriums and the kinetics of other thermaland catalytic reactions in the liquid layer.

The lower activation energies provided by the catalyst also increasesthe efficiency of the delayed coker operation, particularly in the useof heat. In general, the catalyst can be used to perform the same degreeof cracking and coking reactions (catalytically and thermally) with lessheat input or perform more of these endothermic reactions (preferablycracking vs. coking) with the same heat input. In most cases, the latterwould be preferred. In some cases, the catalyst an exemplary embodimentof the present invention would also help promote polymerization coking,a type of exothermic coking that polymerizes the aromatic sheetderivatives of the asphaltenes present in the coker feed. The catalysttends to crack off asphaltene side chains more quickly and efficientlyto allow the derivative aromatic sheets close enough physical proximityto promote their polymerization. All of these thermodynamic and reactionkinetic properties of this new reactor system in the coke drum can havefavorable effects on the heat balance and the temperature profile in thecoke drum during the coking cycle.

With more efficient use of heat and the possible increase in heat in thecoke drum via exothermic reactions, an exemplary embodiment of thepresent invention can favorably affect the temperature profile of thecoke drum. As noted before, the preferred injection option uses thecarrier oil as a quench that reduces vapor overcracking and the excessproduction of low-value gas and creates an internal recycle withintimate contact with the catalyst. Though this causes a slightly lowertemperature at the coke drum outlet, the additional catalytic reactions(e.g. catalytically cracking of traditional recycle components) create adifferent reaction chemistry and chemical equilibrium, that providesimproved product yields (e.g. less fuel gas & more transport fuels) evenwith a slightly lower coke drum outlet temperature. This phenomenon isnot suggested by traditional delayed coking models and operations. Inaddition, the more efficient use of heat and possible exothermicreaction heat may create higher temperatures in the liquid layer, butmore likely is consumed in additional endothermic, thermal reactions.

Reaction Equilibriums, Thermodynamics, and Kinectics:Thermodynamics/Kinetics: Present Invention Vs. Traditional DelayedCoking

All of the analyses above are based on the thermodynamic and kineticprinciples of traditional delayed coking. A fair evaluation of test datashould also consider the impact of the catalyst on thermodynamic andkinetic models for traditional delayed coking processes. After all, thepresence of a catalyst from the an exemplary embodiment of the presentinvention in the delayed coking process can substantially change thechemical reaction mechanisms, the coke drum temperature profile, and thevapor-liquid equilibriums in the coke drum during the coking cycle ofthe traditional delayed coking process.

First and foremost, the properly designed catalyst will lower activationenergies for both cracking and coking reactions in the coke drum duringthe coking cycle. With the an exemplary embodiment of the presentinvention, catalysts can preferentially lower cracking reactionactivation energies by up to one third in repetitive reactions in boththe vapor and liquid phases of the coke drum. With the long residencetime of the coking cycle (hours), each catalyst particle can conceivablyreduce the activation energy for many repetitive cracking reactions inthe vapor and preferably in the liquid phase, until the catalystparticle participates in enough coking reactions to consume it in thecoke. In its preferred embodiment, the present invention also quenchesexcessive cracking of the vapor products (i.e. vapor overcracking) whilecondensing the heaviest recycle components onto the catalyst, creatingan internal recycle and intimate contact with the catalyst to providemore selective use of the catalyst. Since these recycle components arecatalytically cracked to smaller hydrocarbon molecules with higher vaporpressures, most of these traditional recycle components exit the cokedrum even at lower drum outlet temperatures.

In many cases, the catalyst of an exemplary embodiment of the presentinvention will also lower the activation energy for coking reactions inan advantageous manner. For example, certain heavy hydrocarbons in somecoker feeds are resistant to cracking or coking in the strictly thermalreactions environment of the traditional delayed coking process. As thecoking cycle proceeds, these materials tend to increase in concentrationand pool in the liquid layer on top of the coke. At the end of thecoking cycle much of this material has neither cracked or coked, and hasbeen noted to cause problems with dangerous ‘hot spots’ in the decokingcycle. Since these heavy hydrocarbons tend to have a much greaterpropensity to coke (vs. crack), the catalyst of an exemplary embodimentof the present invention (designed to preferentially crack) would stillreduce the activation energy for coking reactions to have this materialcoke, and mitigate ‘hot spot’ issues. In addition, coking thesematerials would also have the advantage of substantially reducing itsconcentration in the liquid layer to improve reaction equilibriums andkinetics of other thermal and catalytic reactions in the liquid layer.

The lower activation energies provided by the catalyst an exemplaryembodiment of the present invention makes the delayed coker operationmore efficient, particularly in the use of heat. In general, thecatalyst could be used to perform the same degree of cracking and cokingreactions (catalytically and thermally) with less heat input or performmore of these endothermic reactions (preferably cracking vs. coking)with the same heat input. In most cases, the latter would be preferred.In some cases, the catalyst of an exemplary embodiment of the presentinvention would also help promote polymerization coking, a type ofexothermic coking that polymerizes the aromatic sheet derivatives of theasphaltenes present in the coker feed. The catalyst tends to crack offasphaltene side chains more quickly and efficiently to allow thederivative aromatic sheets close enough physical proximity to promotetheir polymerization. All of these thermodynamic and reaction kineticproperties of this new reactor system in the coke drum can havefavorable effects on the heat balance and the temperature profile in thecoke drum during the coking cycle.

With more efficient use of heat and the possible increase in heat in thedrum via exothermic reactions, an exemplary embodiment of the presentinvention can favorably affect the temperature profile of the coke drum.As noted before, the preferred embodiment uses the carrier oil as aquench that reduces vapor overcracking and the excess of low-value gasand creates an internal recycle with intimate contact with the catalyst.Though this causes a lower temperature at the coke drum outlet, theadditional catalytic reactions (e.g. catalytically cracking traditionalrecycle components) create a different reaction chemistry and chemicalequilibrium, that provides improved product yields (e.g. less fuel gas &more transport fuels) even with a lower coke drum outlet temperature.This phenomenon would not be suggested by traditional delayed cokingmodels. In addition, the more efficient use of heat and possibleexothermic reaction heat may create higher temperatures in the liquidlayer, but more likely would be consumed in additional endothermic,thermal reactions. If the temperature would become too high for anyreason, the outlet temperature of the coker feed heater could be cutback slightly and gain associated operational and maintenance benefits.

The catalyst of an exemplary embodiment of the present invention in thedelayed coking process not only favorably changes the reactionmechanisms and the temperature profile, but may also favorably impactsthe chemical reaction equilibriums and kinetics. As noted above, thecatalytic cracking of traditional recycle components to smallermolecules with higher vapor pressures changes the vapor-liquidequilibrium at the coke drum outlet in such a way that these materialsstill exit the coke drum, even at lower coke drum exit temperatures. Inaddition, the catalytic coking of the feed components that resistthermal cracking or thermal coking reduces the concentration of thesematerials in the liquid layer, improving the chemical reactionequilibriums and kinetics for other thermal and catalytic cracking orcoking reactions. Other examples of improved chemical reactionequilibriums and kinetics exist, as well.

In conclusion, traditional thermodynamic models of the delayed cokingprocess may not be sufficient to accurately predict what happens in thedelayed coking process using an exemplary embodiment of the presentinvention due to the factors described above. These traditional cokermodels will not likely have accurate thermodynamic assumptions (vectors)as well as reaction activation energies. These traditional thermodynamiccoker models may need to be modified with additional vectors or modifiedcoefficients to address the substantially different chemical reactionsand environment associated with an exemplary embodiment of the presentinvention.

The catalyst of an exemplary embodiment of the present invention in thedelayed coking process not only favorably changes the reactionmechanisms and the temperature profile, but also favorably impacts thechemical reaction equilibriums and kinetics. As noted above, thecatalytic cracking of traditional recycle components to smallermolecules with higher vapor pressures changes the vapor-liquidequilibrium at the coke drum outlet in such a way that these materialsstill exit the coke drum, even at slightly lower coke drum exittemperatures. In addition, the catalytic coking of the feed componentsthat resist thermal cracking or thermal coking reduces the concentrationof these materials in the liquid layer, improving the chemical reactionequilibriums and kinetics for other thermal and catalytic cracking orcoking reactions. Other examples of improved chemical reactionequilibriums and kinetics include better reaction conditions forcatalytic cracking of aromatics.

In conclusion, an exemplary embodiment of the present inventionintroduces an active catalyst to the delayed coking process in a mannerthat substantially changes the chemical reactions and environment.

In addition to the novel features and advantages mentioned above, otherbenefits will be readily apparent from the following descriptions of thedrawings and exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of an example of catalyst effect in an exemplaryembodiment of the present invention.

FIG. 2 is a schematic of a traditional delayed coking process. U.S. Pat.No. 8,372,265 and U.S. Pat. No. 8,372,264 have similar figures with adescription of the numbered components, their function, and theirinteraction (how they operate together).

FIG. 3 is a schematic of an exemplary embodiment of a system of thepresent invention that may be adapted to use hydrogen or hydrogengenerating compound(s) to enhance catalytic reactions. In this exampleof the present invention, the traditional delayed coking process ismodified to incorporate a means of introducing hydrogen or hydrogengenerating compound(s) to the primary reaction zones of the coke drum(preferably the liquid layer) during the coking cycle to enhance thecatalytic reactions, caused by the injection of a catalytic additiveabove the liquid solid interface. The catalytic additive injectionsystem consists of a means (210) to mix the desired catalytic components(e.g. heated mix tank with mechanical mixers) in a batch or continuousmode. The desired catalytic components consist of catalyst(s) alone orin combination with seeding agent(s) 220, excess reactant(s) (222),quenching agent(s) (224), carrier fluid(s) (226) or any combinationthereof. Means of controlling the temperature, pressure, and flow rateare provided to regulate the injection of the additive into the cokedrum above the vapor/liquid interface in the coke drum during the cokingcycle. In addition, hydrogen and/or hydrogen generating compound(s) areoptionally injected (218) into the coker feed between the fractionatorand the process heater, in the heater, between the heater and the cokedrum, or any combination thereof. The hydrogen and/or hydrogen releasedis then transferred to the primary reaction zone in the coke drum(preferably the liquid layer) to enhance catalytic reactions (preferablycracking reactions). In this manner, the coke yields are reduced furtherrelative to the prior art and liquid yields are increased furtherrelative to the prior art.

FIG. 4 is a schematic of an exemplary embodiment of a system of thepresent invention that may be adapted to use hydrogen or hydrogengenerating compound(s) via a modified drill stem to enhance catalyticreactions. In this example of the present invention, the traditionaldelayed coking process is modified as in FIG. 3, but with an additionaloption to use a modified drill stem to inject the catalytic additiveand/or the hydrogen/hydrogen generating compound(s) to the primaryreaction zones of the coke drum (preferably the liquid layer) during thecoking cycle. In this exemplary embodiment, the modified drill stemfollows the rising liquid layer (e.g. with a safe distance above)throughout the coking cycle to enhance the catalytic reactions, causedby the injection of a catalytic additive above the liquid solidinterface. Again, several options (218) exist for the introduction ofthe hydrogen/hydrogen generating compound(s).

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENT(S)

Catalyst Benefits in a Delayed Coker:

In this section, the benefits of catalyst in a delayed coker arediscussed. First, the definition of a catalyst is a substance thatincreases the rate of a chemical reaction by reducing the activationenergy, preferably without being consumed by the reactions. Catalystscan be a solid, a liquid, and/or a gas, and normally is not changed bythe reaction process. In FIG. 1, catalyst effect is illustrated withover 30% reduction in the activation energy. Thus, an effective catalystin a delayed coker reduces the amount of energy required to complete thesame reactions that occur via strictly thermal reactions (vs. catalyticreactions) in the traditional delayed coker. As a result, an effectivecatalyst in a delayed coker can be used to (1) maintain the same levelof chemical reactions with lower energy input or (2) increase the levelof chemical reactions with the same energy input.

In the traditional delayed coking process, most of the chemicalreactions occur in the coke drums. Cracking, Coking, Polymerization,Hydrogenation, and Dehydrogenation reactions occur to a certain degree.Of these, cracking and coking are the predominant reactions. Thereaction mechanisms in the cracking and coking reactions are similar,with both being endothermic, free-radical reactions. Again, theintroduction of an effective catalyst will reduce the energy required tocomplete these reactions.

In the traditional delayed coking process, complex chemical changesoccur in the coke drums. Competing chemical reactions can basicallyclassified into thermal cracking reactions and various type of cokingreactions. The thermal cracking reactions can be further classified intothermal liquids cracking and thermal vapor overcracking. Thermal liquidscracking is basically the thermal cracking of very heavy hydrocarbons inthe coker feed to gas oils, naphtha, PPs (Propanes & propenes), and BBs(butanes and butenes), which are typically the most valuable products inthe coker. Thermal vapor overcracking is basically the excessive thermalcracking of these valuable products to lower valued fuel gas. Cokingreactions can be classified into thermal coking, asphaltic coking, andpolymerization coking. Thermal coking is purely endothermic, freeradical condensation of heavy hydrocarbons (typically aromatic) to formneedle coke. Asphaltic coking are isothermic reactions, involving thedesolutation of asphatenes from the cracking of their solvent(resins/aromatic oils), resulting in shot coke. The combination ofthermal coking and asphaltic coking results in sponge coke. The ratio ofasphaltic to thermal coking determines the degree of sponge vs. shotcoke, which depends on the chemical composition of the reactantsinvolved. Finally, polymerization coking is an exothermic cokingreaction that results in shot coke or dense sponge coke, depending onthe characteristics of the reactants.

Coking reactions can be classified into thermal coking, asphalticcoking, and polymerization coking. Thermal coking is purely endothermic,free radical condensation of heavy hydrocarbons (typically aromatic) toform needle coke. Asphaltic coking are isothermic reactions, involvingthe desolutation of asphaltenes from the cracking of their solvent(resins/aromatic oils), resulting in shot coke. The combination ofthermal coking and asphaltic coking results in sponge coke. The ratio ofasphaltic to thermal coking determines the degree of sponge vs. shotcoke, which partially depends on the chemical composition of thereactants involved. That is, a low ratio produces sponge coke; highratio produces shot coke; and near zero produces needle coke, from ahighly aromatic coker feed with minimal asphaltene content. Finally,polymerization coking is an exothermic coking reaction that results inshot coke or dense sponge coke, depending on the characteristics of thereactants.

Polymerization coking can occur with coker feeds having high asphaltenecontent. The macrostructure of asphaltenes vary considerably, but can becharacterized by layers of aromatic sheets that are connected byaliphatic chains. In traditional delayed coking, the thermal cracking ofthe asphaltenes is somewhat slow and inefficient, leaving aliphaticchains on the aromatic sheets. That is, the asphaltene derivatives inthe traditional delayed coker typically retain sufficient aliphaticchains that don't allow the aromatic sheets to get close enough with theproper orientation to promote polymerization coking. As such, theresidual aliphatic chains keep the aromatic sheets separated and preventpolymerization coking coking. In the presence of effective catalyst(s),the activation energy for the initial cracking of asphaltenes issignificantly reduced. Thus, catalytic cracking significantly increasesthe speed and efficiency of removing aliphatic side chains from thearomatic sheets of the asphaltenes. As a result, the aromatic sheets canachieve the proper distance (e.g. <4 A°) and orientation to increasepolymerization coking significantly.

In the present invention, introducing an effective catalyst to theproper reaction zones modifies the reaction chemistry and creates a newset of competing reactions in the coke drum of the delayed cokingprocess during the coking cycle. In this manner, the present inventionadds catalytic cracking and catalytic coking, as well as polymerizationcoking in the coke drums.

If the heat input remains constant, the catalyst reduces the amount ofheat required to complete the same reactions that occur in thetraditional delayed coker with only thermal reactions (vs. catalytic).As such, the catalytic cracking reduces the amount of heat used inthermal cracking making it available for additional reactions orincrease temperature in the drum. Additional reactions, preferablycatalytic cracking vs. thermal cracking and thermal coking, would likelyoccur.

As discussed previously, catalytic cracking of asphaltenes and theirderivatives promotes exothermic polymerization coking that will increasethe heat available for additional reactions or increase localtemperatures. This increase in polymerization coking will likelydecrease the levels of endothermic, thermal coking and isothermic,asphaltic coking of the traditional coker. Thus, the promotion ofpolymerization coking (caused by the efficient catalytic cracking ofasphaltenes and their derivatives) has an added benefit of additionalheat for additional endothermic reactions: catalytic cracking, thermalcracking, catalytic coking, and thermal coking.

Even catalytic coking can be very advantageous relative to thetraditional delayed coking process. That is, catalytic coking reducesthe amount of energy that would otherwise be needed in thermal coking,increasing heat available for other reactions to be completed.

In addition, an effective catalyst of the current invention can cause asignificant reduction in coke hot spots, a dangerous operational problemat many delayed coking units handling troublesome coker feeds.Apparently, this happens when: (1) Certain liquid compounds from thecoker feed or derivatives of other chemical compounds have highactivation energies that do not allow either cracking or coking. (2)These chemicals tend to increase in concentration in the liquid layerthroughout the coking cycle, and reduce the concentration of otherchemical compounds that would normally have activation energies that aresufficiently low to crack or coke but their concentration has beenlowered by the chemical compounds of item (1) and these reactions areinhibited. (3) Chemical compounds (regardless of source) that do notcrack or coke during the coking cycle may have vapor pressures thatdon't allow them to escape the coke drum. Thus, these chemical compoundstend to remain liquid as the coke cools and form hot spots in the coke,when cooling media comes in contact with masses of these chemicalcompounds (4) Thus, the presence of the appropriate catalyst can lowerthe activation energies to allow coking or preferably cracking of thesematerials before the end of the coking cycle and substantially reducecoke hot spots. Also, the reduction of these materials (Caused by aneffective catalyst) is believed to cause indirect, positive impacts(reducing the concentration of essentially inert chemicals in the liquidlayer) on chemical equilibriums of certain chemical reactions,increasing the driving force for these favorable reaction improving thecompletion of cracking and coking reactions. In this manner, evencatalytic coking can be helpful in the coke drum.

As discussed previously, effective catalyst(s) of the present invention(introduced to the coke drum of the delayed coker during the cokingcycle) cause reduction of activation energies for either coking andpreferably cracking reactions. These catalytic cracking and catalyticcoking reaction require substantially less heat (e.g. 30%) than theirthermal cracking and thermal coking counterparts in the traditionaldelayed coker for the same reactions. With the potential increase inheat available from the exothermic polymerization coking, the netincrease in available heat can increase the liquid temperature,particularly for the same levels of cracking and coking. Preferably, theadditional heat available will be used in additional cracking reactionsin most cases, instead of increasing the liquid layer temperature.

In summary, the basic benefit of introducing effective catalyst(s) inthe primary reaction zones of the coke drum of the delayed cokingprocess during its coking cycle is the increase in available heat in thecoke drum, primarily the liquid layer. This increase in available heatwill likely lead to an increase in coke drum temperature and/or asignificant increase in endothermic chemical reactions of heavyhydrocarbons in the liquid/foaming layers that would otherwise form cokeinto lighter hydrocarbon products of higher value.

As will be seen later, incremental catalyst addition (e.g. 0.1-0.3 wt. %of coker feed) creates incremental improvements in conversion of cokeyields to higher yields of gas oils, naphtha, and/or Liquid PetroleumGas (LPG), consisting of PPs and BBs. The optimal amount of catalystwill depend on many factors at each refinery, including catalyst costs.Commercial demonstrations of the present invention with the use ofrefinery Linear Programming (LP) model will be most productive indetermining the most effective catalyst and proper usage.

Also, not just any catalyst will work. In fact, off the shelf FCCUcatalysts with substantial zeolite concentrations (e.g. high Z/M ratios)will likely be counterproductive. That is, high activity and small poresize (e.g. 6-9 microns) in any catalyst will likely cause more crackingof lighter liquids to less valuable gasses. For example, a normal FCCUcatalyst would likely crack LCGO to fuel gas. In addition, the bestperforming catalyst (higher yields conversion) with higher costs may notbe the most cost effective catalyst.

Primary Advantages of Exemplary Embodiments of the Present Invention:

Advantages of exemplary embodiments of the present invention include itsuse of various process options, system design, and operating flexibilityto maximize value for each refinery, according to its LP model results.Of course, refinery models vary considerably from refinery to refinerydue to various factors, including refinery process configuration, crudeslate, etc. Within the delayed coker, the maximum value typicallyincludes (1) maximizing cracking (thermal & catalytic) of the coker feedand its derivatives that would otherwise form coke, (2) minimizingconversion (e.g. vapor overcracking) of gas oils and coker naphtha tolow-value fuel gases (e.g. fuel gas), and (3) maximizing cracking oftraditional recycle components on the first pass to reduce externalrecycle. Finally, it should be noted that an exemplary embodiment of thepresent invention may not create a mini fluid catalytic cracking unit(FCCU) in the coker. Most refineries already have sufficient capacity tocrack gas oils to naphtha in a more efficient manner, the FCCU. However,it is recognized that many of the same reactions that occur in an FCCUwill also occur in the present invention, and some of them are notdesirable (e.g. consuming catalyst activity for reactions that the FCCUperforms more efficiently). In contrast, a major focus of an exemplaryembodiment of the present invention may be catalytic cracking of theheavier hydrocarbons (not necessarily aromatic in nature or the highestboiling point compounds) in the gas and liquid phases that wouldotherwise form coke

In order to achieve the maximum value, the catalyst(s) must be usedefficiently. In this regard, an advantage of an exemplary embodiment ofthe invention is to introduce effective, active catalyst(s) with thedesired characteristics to the liquid and foaming layers. At the sametime, the exposure of the active catalyst to the vapors needs to beoptimized. The conversion of gas oils and naphtha to lower value fuelgas must be limited. However, an increase in olefins production (PPs andBBs) can be very advantageous in many refineries with LPG recovery ornearby chemical plants that require light olefins as feedstocks. Inaddition, an increase in light olefins (e.g. higher octane) may helpimprove coker naphtha quality and value.

Desired characteristics for the optimal catalyst(s) are not limited to aparticular type of catalyst. In fact, the present invention anticipatesthat effective catalyst(s) may be developed for this purpose. Keyfactors should be considered

(1) Catalyst with higher porosity for intimate contact with largerhydrocarbons (and maintain passageways for cracked components). In thisregard, Lower Z/M ratio is often preferable. Due to different reactionconditions in the coker liquid layer (e.g. the longer residence time,temperature, etc.), the traditional relationship of Z/M in the FCCU donot necessarily apply in this application.

(2) Due to the difference in chemical reaction conditions, the optimalactivity level of the catalyst will likely be different (vs. FCCU) forvarious chemical compounds (e.g. chemical equilibrium for the crackingof aromatics is often favored at lower temperatures (800-850° F.) andlonger residence time).

(3) Inexpensive catalysts can include regeneration and/or treatment ofused catalysts. For example, FCCU catalysts (Particularly for heavyfeeds) are typically regenerated before being flushed from the unit asequilibrium catalyst (e.g. as fresh catalyst is added). Also, thisequilibrium catalyst can be further treated (e.g. thermally) to increasethe porosity for the larger hydrocarbon molecules.

(4) Catalyst fluidization in the liquid layer can maximize residencetime (e.g. contact with fluids). The liquid layer in the delayed cokertends to be fairly turbulent due to the velocity of the product vaporsand liquids as they rise through the restricted flow areas at the top ofthe coke (e.g. branches). As a result, catalyst that has characteristics(e.g. density, particle size distribution (PSD), etc.) to maintainfluidization are preferable. Optimal PSD is preferable to maintainfluidization vs. product vapor entrainment.

In many cases, off the shelf catalysts can be counterying productive.For example, FCCU catalyst with high Z/M ratios has low porosity that ismore conducive to creating excessive vapor overcracking than crackingvery heavy hydrocarbons.

Preventing catalyst entrainment in the coker product vapors is usually amajor concern with refineries. Characteristics of the catalyst(s) andinjection are key. Most commercial cokers are designed with very lowvapor velocity in the upper drum to create a disengagement section tolimit the entrainment of coke fines. In many cases, catalyst withsufficient density can inhibit catalyst entrainment by classifyingcatalyst size over 60 microns. In addition, injection nozzle design andoperating conditions can play a substantial role in limitingentrainment. Injection nozzle manufacturers can use Computational FluidDynamics to determine the proper catalyst size and injectioncharacteristics to minimize carryover. Other tests can also be used forassistance in injection nozzle design.

As is common with many patent applications, this application seeks thebroadest coverage that distinguishes over the known art. A preferredembodiment may be viewed to be a most favorable application of thepresent invention. Various other embodiments are provided as alternativemeans to achieve the stated advantages of exemplary embodiments of thepresent invention.

In previous patents by this inventor, broad coverage of various facetshas been achieved. Previous patents have covered a combination ofvarious components in the catalytic additive. Also, a variety ofcatalyst types and treatments have been covered, along with a variety ofprocess options and locations for the additive additions. A chemicalmeans of adding the additive has been shown to be effective in gettingthe active catalyst to the desired reaction zones, without creation ofexcess fuel gas. In exemplary embodiments of the present invention, amechanical means of introducing the catalytic additive directly to theprimary reaction zone (preferably in the liquid layer) of the coke drumand introducing hydrogen and/or hydrogen generating compounds into thosesame primary reaction zones to substantially enhance the catalyticreactions caused by the introduction of the catalytic additive to thecoke drum of the delayed coking process during the coking cycle.

The chemical means of adding active catalyst(s) to the liquid/foaminglayers uses a carrier oil that acts as a quench to limit the exposure ofthe product vapors to the active catalyst(s). The localized quenchcaused by the partial evaporation of this carrier oil does two things.First, it condenses the heaviest hydrocarbons on the catalyst, (whichact as a seeding agent) creating intimate contact between thetraditional recycle materials (e.g. target reactants) and the catalyst,increasing selectivity of the catalyst reactions. This condensed recyclematerial also serves to protect the active catalyst until it settles tothe liquid layer, where the condensed recycle materials tend torevaporize and crack to smaller, more valuable hydrocarbons. Secondly,this localized cooling quenches (thermally and chemically) the vaporovercracking reactions and minimizing the conversion of gas oils andnaphtha to excessive fuel gas.

In an example of a preferred embodiment, the catalyst with the condensedrecycle components settle to the liquid layer, which is significantlyhotter than the product vapors above it. As such, the heavy recyclecomponents tend to revaporize and catalytically crack to significantlysmaller hydrocarbons that have sufficiently higher vapor pressures toexit the coke drum even with lower drum outlet temperatures. In thismanner, the quench effect of the carrier oil favorably impacts tworeaction mechanisms and changes the reaction equilibriums, kinetics andthermodynamics.

Even after cracking these traditional recycle components, the catalystwill typically continue to settle into the liquid layer that hassufficient turbulence to keep the properly designed catalyst(s) in afluidized state for significant portions of time. With this longerresidence time, the catalysts will likely have sufficient contact andtime to promote catalytic cracking of other heavy hydrocarbons thatwould otherwise form coke.

In the implementation of an example of a preferred embodiment, properinjection of the catalytic additive into the coke drum above the liquidlayer is key to create the contact and proper conditions for the desiredcatalytic reactions.

Thus, an example of a preferred embodiment of the present inventionfavorably modifies the reaction chemistry in the coke drum of thetraditional delayed coking process. First, the condensation of thetraditional recycle components onto the catalyst creates and internalrecycle that causes catalytic cracking of this recycle materials.Second, the intimate, turbulent contact with the heavy hydrocarbons inthe liquid/foam layers, causing catalytic cracking of feed componentsthat would otherwise form coke. Thirdly, catalytic coking of heavyhydrocarbons that normally resists both cracking and coking cansignificantly reduce ‘coke hot spots.’ Both catalytic cracking andcatalytic coking make more heat available for additional cracking andcoking reactions, both thermal and catalytic. Finally, the quench effectalso reduces vapor overcracking, creating less fuel gas and more gasoils and naphtha.

In the preferred embodiment of the present invention, the changes inreaction chemistry (e.g. equilibriums) changes the traditional cokerrelationship between product distribution and drum outlet temperature.In the traditional delayed coking operation, the drum outlet temperatureis controlled to the highest level possible with a given heat balance.This is done to maintain the process equilibrium that provides highestlevel of gas oil and recycle escaping the coke drum and avoiding cokeformation. However, the introduction of catalyst changes this processequilibrium by lowering the activation energy required to crack thetraditional recycle components. Thus, the traditional recycle (withintimate catalyst contact) cracks to smaller, lighter hydrocarbons thehave a high enough vapor pressure to exit the coke drum even at lowercoke drum outlet temperatures. Finally, the quench reduces vaporovercracking by terminating undesirable thermal cracking reactions.

Based on actual data from a test run in a west coast U.S. refinery, thequench effect is roughly 10.7° F. for every 1 wt. % of the coker feed.This was based on 1700 BPD of Light Coker Gas Oil (LCGO) used in thevapor line quench in a 52,100 BPD of coker feed. In this case, the drumoutlet temperature was cooled from 806° F. to a fractionator inlettemperature of 771° F.

The preferred carrier oils with their estimated quench effect are shownbelow:

FCCU Decanted Slurry Oil: Available at 30% U.S.

Chemically Inert?: <60% Vaporized: <6° F./1 Wt. %

FCCU Heavy Cycle Oil: Available at >75% U.S.?

Chemically Inert?: >85% Vaporized: 9° F./1 Wt. %

Heavy Coker Gas Oil: Available at 100% U.S.

Loss of Activity: 100% Vaporized: 10.7° F./1 Wt. %

If needed, the vapor line quench is reduced to offset this coke drumquench and maintain proper heat balance in the delayed coking units.

Another way of evaluating the change in the traditional relationship ofcoke drum outlet temperature and coker product distribution is toestimate the change in coke drum outlet temperature for the same levelof cracking and coking reactions. That is, the coke drum outlettemperature would actually go up at a constant yield rate due to theexcess heat available from the reduction in activation energiesattributed to the catalyst(s).

The drum outlet temperature can be estimated by calculating the heat inthe feed which is primarily dependent on the heater outlet temperature.In the traditional coking unit, the coke drum outlet temperature isroughly determined by the heat in the feed minus the heat absorbed bythe endothermic reactions and add the heat gained from exothermicpolymerization coking. In the preferred embodiment of the presentinvention, the catalytic cracking and catalytic coking absorbs less heatthan the thermal cracking and thermal coking, and exothermic heat frompolymerization coking is more likely to be gained. Thus, the coke drumoutlet temperature would be higher for a constant reaction rate.

In conclusion, the net effect of the preferred embodiment of the presentinvention is very positive. That is, the increase in LP Model value fromthe changes in product distribution far outweigh the negative impact ofdecreasing the coke drum outlet temperatures. This was confirmed in thepilot plant studies, where improved product yields were achieved despitedrum outlet temperatures reduced by >15° F. due to the carrier oilquench effect.

Additive Package

Exemplary embodiments of the present invention typically include anadditive package to be injected in the coke drum of a delayed cokingprocess, during the coking cycle. Said additive package comprises of (1)catalyst(s), (2) seeding agent(s), (3) excess reactant(s), (4) quenchingagent(s), (5) carrier fluid(s), or (6) any combination thereof. Theoptimal design of additive package may vary considerably from refineryto refinery due to differences including, but not limited to, coker feedblends, coking process design & operating conditions, coker operatingproblems, refinery process scheme & downstream processing of the heavycoker gas oil, and the pet coke market & specifications.

In view of the foregoing description, the following presents furtherdetailed description of exemplary embodiments of the present invention.This description of exemplary embodiments is divided into two majorsubjects: General Exemplary Embodiment and Other Embodiments. Theseembodiments discuss and demonstrate the ability to modify (1) thequality or quantity of the additive package and/or (2) change the cokingprocess operating conditions to optimize the use of an exemplaryembodiment of the present invention to achieve the best results invarious coking process applications.

Description and Operation of Exemplary Embodiments of the InventionGeneral Exemplary Embodiment

Description of Drawings:

FIG. 3 provides a visual description of an exemplary embodiment of thepresent invention in its simplest form. This basic process flow diagramshows a heated, mixing tank (210) (as an exemplary means of mixing andmeans of controlling temperature) where components of an example of thepresent invention's additive may be blended: catalyst(s) (220), seedingagent(s) (222), excess reactant(s) (224), carrier fluid(s) (226), and/orquenching agent(s) (228). Obviously, if the additive package iscomprised of only one or two of these components, the need for a heated,mixing tank or other means of mixing and temperature control can bereduced or eliminated. The mixed additive (230) is then injected into ageneric coking vessel (240) above the vapor/liquid-solid interface viaproperly sized pump(s) (250) (as an exemplary means of pressurizedinjection) and piping, preferably with properly sized, atomizinginjection nozzle(s) (260). In this case, the pump is controlled by aflow meter (270) with a feedback control system relative to thespecified set point for additive flow rate. In an exemplary embodimentof the present invention, the primary purpose of this process is toconsistently achieve the desired additive mixture of components andevenly distribute this additive throughout the cross sectional area ofthe coking vessel to provide adequate contact with the product vapors,(rising from the vapor/liquid interface) to quench the vapors (e.g.2-15° F.) and condense the heavy hydrocarbons onto the catalyst orseeding agent. Much of the additive slurry, particularly the quenchingagent(s), will vaporize upon injection, but heavier liquids (e.g. excessreactants) and the solids (e.g. catalyst) would be of sufficient size togradually settle to the vapor/liquid interface, creating the desiredeffect of selectively converting the highest boiling point components ofthe product vapors. In general, an exemplary system could be designed to(1) handle the process requirements at the point(s) of injection and (2)prevent entrainment of the additive's heavier components (e.g. catalyst)into downstream equipment. Certain characteristics of the additive(after vaporization of lighter components) will be key factors tominimize entrainment: density, particle size of the solids (e.g. >40microns) and atomized additive droplet size (e.g. 50 to 150 microns).

The specific design of this system and the optimal blend of additivecomponents will vary among refineries due to various factors. Theoptimal blend may be determined in pilot plant studies or commercialdemonstrations of this invention (e.g. using an existing anti-foamsystem, modified for higher flow rate). Once this is determined, oneskilled in the art may design an exemplary system to reliably controlthe quality and quantity of the additive components to provide aconsistent blend of the desired mixture. This may be done on batch orcontinuous basis. One skilled in the art may also design and developoperating procedures for the proper piping, injection nozzles, andpumping system, based on various site specific factors, including (butnot limited to) (1) the characteristics of the additive mixture (e.g.viscosity, slurry particle size, etc.), (2) the requirements of theadditive injection (e.g. pressure, temperature, etc.) and (3) facilityequipment requirements in their commercial implementation (e.g.reliability, safety, etc.).

Description of Additive:

The additive in an exemplary embodiment of the present invention may bea combination of components that have specific functions in achievingthe utility of the respective exemplary embodiment. As such, theadditive is not just a catalyst in all applications of the presentinvention, though it can be in many of them. In some embodiments, theremay be no catalyst at all in the additive. In certain applications, anembodiment of the present invention would use a quench agent to quenchthe vapor overcracking in the product vapors to decrease the productionof low value fuel gas. In other applications, another embodiment of thepresent invention would include the injection of only quench agent(s)and/or carrier fluid(s) that may improve the distillate yield of thecoking process. Thus, the term ‘catalytic additive’ does not apply inall embodiments, but could in many embodiments. The following discussionprovides further breadth of the possible additive components, theirutility, and potential combinations.

Said additive package comprises of (1) catalyst(s), (2) seedingagent(s), (3) excess reactant(s), (4) quenching agent(s), (5) carrierfluid(s), or (6) any combination thereof. The optimal design of additivepackage may vary considerably from refinery to refinery due todifferences including, but not limited to, coker feed blends, cokingprocess design & operating conditions, coker operating problems,refinery process scheme & downstream processing of the heavy coker gasoil, and the pet coke market & specifications.

Catalyst(s):

In general, the catalyst comprises any chemical element(s) or chemicalcompound(s) that reduce the energy of activation for the initiation ofthe catalytic cracking or catalytic coking reactions of the high boilingpoint hydrocarbons (e.g. heavy coker gas oil or side chains ofpolycyclic aromatic hydrocarbons:) in the product vapors and liquidlayer in the coke drum. In general, the catalyst(s) may be a solid, aliquid, a gas, and/or a multi-phase component. The catalyst may bedesigned to favor cracking (preferably) or coking reactions and/orprovide selectivity in the types of heavy hydrocarbons that are crackedor coked. For the sake of this discussion throughout the Description,‘heavy hydrocarbons’ refer to hydrocarbons that are heavier than atleast the highest 50 weight percent (e.g. boiling point of simulateddistillation laboratory results) of the heavy coker gas oil with averageboiling points exceeding 700 degrees Fahrenheit. In addition, thecatalyst may be designed to aid in coking heavy hydrocarbons to certaintypes of coke, including coke morphology, quality & quantity of volatilecombustible materials (VCMs), concentrations of contaminants (e.g.sulfur, nitrogen, and metals), or combinations thereof. Finally, thecatalyst may be designed to preferentially coke via an exothermic,asphaltene polymerization reaction mechanism (vs. endothermic,free-radical coking mechanism). In this manner, the temperature in thecoke drum may increase, and potentially increase the level of thermaland/or catalytic cracking or coking.

In an exemplary embodiment of the present invention, characteristics ofthis catalyst typically include a catalyst substrate with a chemicalcompound or compounds that perform the function stated above. In manycases, the catalyst will have acid catalyst sites that initiate thepropagation of positively charged organic species called carbocations(e.g. carbonium and carbenium ions), which participate as intermediatesin the coking and cracking reactions. Since both coking and crackingreactions are initiated by the propagation of these carbocations,catalyst substrates that promote a large concentration of acid sites aregenerally appropriate. Also, the porosity characteristics of thecatalyst would preferably allow the large, aromatic molecules easyaccess to the acid sites (e.g. Bronsted or Lewis). For example, fluidcatalytic cracking catalyst for feeds containing various types ofresidua often have higher mesoporosity to promote access to the activecatalyst sites. In addition the catalyst is preferably sizedsufficiently large (e.g. >40 microns) to avoid entrainment in the vaporsexiting the coke drum. Preferably, the catalyst and condensed heavyhydrocarbons have sufficient density to settle to the vapor/liquidinterface. In this manner, the settling time to the vapor/liquidinterface may provide valuable residence time in cracking the heavyhydrocarbons, prior to reaching the vapor/liquid interface. For heavyaromatics with the high propensity to coke, catalytic coking may takeplace during this settling period and/or after reaching the vapor/liquidinterface. At the vapor/liquid interface, an active catalyst maypreferably continue promoting catalytic cracking (preferably) and/orcoking reactions to produce desired cracked liquids and coke (e.g.asphaltene polymerization). Sizing the catalyst (e.g. 40 to >200microns) to promote fluidization for the catalyst in the coking vesselmay enhance the residence time of the catalyst in the vapor zone.

Many types of catalysts may be used for this purpose. Catalystsubstrates may be comprised of various porous natural or man-madematerials, including (but should not be limited to) alumina, silica,zeolite, activated carbon, crushed coke, or combinations thereof. Thesesubstrates may also be impregnated or activated with other chemicalelements or compounds that enhance catalyst activity, selectivity, orcombinations thereof. These chemical elements or compounds may include(but should not be limited to) nickel, iron, vanadium, iron sulfide,nickel sulfide, cobalt, calcium, magnesium, molybdenum, sodium,associated compounds, or combinations thereof. For selective coking, thecatalyst will likely include nickel, since nickel strongly enhancescoking. For selective cracking, many of the technology advances forselectively reducing coking may be used. Furthermore, increased levelsof porosity, particularly mesoporosity, may be beneficial in allowingbetter access by these larger molecules to the active sites of thecatalyst. Though the catalyst in the additive may improve cracking ofthe heavy hydrocarbons to lighter liquid products, the catalystultimately ends up in the coke. As such, the preferred catalystformulation would initially crack heavy hydrocarbons to maximize lightproducts (e.g. cracked liquids) from gas oil ‘heavy tail’ components,but ultimately promote the coking of other heavy aromatics to alleviatepitch materials (with a very high propensity to coke vs. crack) in thecoke that cause ‘hot spots.’ It is anticipated that various catalystswill be designed for the purposes above, particularly catalysts toachieve greater cracking of the highest boiling point materials in theliquid layer in the coke drum and coking process product vapors. Withcertain chemical characteristics of these materials and properlydesigned catalysts, substantial catalytic conversion of these materialsto cracked liquids may be accomplished (e.g. >50 Wt. %).

The optimal catalyst or catalyst combinations for each application willoften be determined by various factors, including (but not limited to)cost, catalyst activity and catalyst selectivity for desired reactions,catalyst size, and coke specifications (e.g. metals). For example, cokespecifications for fuel grade coke typically have few restrictions onmetals, but low cost may be the key issue. In these applications, spentor regenerated FCCU catalysts or spent, pulverized, and classifiedhydrocracker catalysts (sized to prevent entrainment) may be the mostpreferred. On the other hand, coke specifications for anode grade cokeoften have strict limits for sulfur and certain metals, such as iron,silicon, and vanadium. In these applications, cost is not as critical.Thus, new catalysts designed for high catalyst activity and/orselectivity may be preferred in these applications. Alumina or activatedcarbon (or crushed coke) impregnated with nickel may be most preferredfor these applications, where selective coking is desirable.

The amount of catalyst used will vary for each application, depending onvarious factors, including the catalyst's activity and selectivity, cokespecifications and cost. In many applications, the quantity of catalystwill be less than 15 weight percent of the coker feed. Most preferably,the quantity of catalyst would be between 0.05 weight percent of thecoker feed input to 3.0 weight percent of the coker feed input. Abovethese levels, the costs will tend to increase significantly, withdiminishing benefits per weight of catalyst added. As described, thiscatalyst may be injected into the vapors in the coking vessel (e.g.above the vapor/liquid interface in the coke drum during the cokingcycle of the delayed coking process) by various means, includingpressurized injection with or without carrier fluid(s): hydrocarbon(s),oil(s), inorganic liquids, water, steam, nitrogen, or combinationsthereof.

Injection of cracking catalyst alone may cause undesirable effects inthe coker product vapors. That is, injection of a catalyst withoutexcess reactant(s), quenching agent(s), or carrier oil(s), may actuallyincrease vapor overcracking and cause negative economic impacts.

Seeding Agent(s):

In general, the seeding agent comprises any chemical element(s) orchemical compound(s) that enhance the formation of coke by providing asurface for the coking reactions and/or the development of cokecrystalline structure (e.g. coke morphology) to take place. The seedingagent may be a liquid droplet, a semi-solid, solid particle, or acombination thereof. The seeding agent may be the catalyst itself or aseparate entity. Sodium, calcium, iron, and carbon particles (e.g.crushed coke or activated carbon) are known seeding agents for cokedevelopment in refinery processes. These and other chemical elements orcompounds may be included in the additive to enhance coke development inthe coking vessel, if appropriate.

The amount of seeding agent(s) used will vary for each application,depending on various factors, including (but not limited to) the amountof catalyst, catalyst activity and selectivity, coke specifications andcost. In many applications, catalytic cracking will be more desirablethan catalytic coking. In these cases, seeding agents that enhancecatalytic coking will be minimized, and the catalyst will be the onlyseeding agent. However, in some cases, little or no catalyst may bedesirable in the additive. In such cases, the amount of seeding agentwill be less than 15 weight percent of the coker feed. Most preferably,the quantity of seeding agent would be between 0.05 weight percent ofthe coker feed input to 3.0 weight percent of the coker feed input. Inmany cases, the amount of seeding agent is preferably less than 3.0weight percent of the coker feed. As described, this seeding agent maybe injected into the coking vessel (e.g. above the vapor/liquidinterface in the coke drum during the coking cycle of the delayed cokingprocess) by various means, including (but not limited to) pressurizedinjection with or without carrier fluid(s): hydrocarbon(s), oil(s),inorganic liquids, water, steam, nitrogen, or combinations thereof.

Excess Reactant(s):

In general, the excess reactant comprises of any chemical element(s) orchemical compound(s) that react with the heavy hydrocarbons to promote acatalytic cracking mechanism and/or to form petroleum coke. In theadditive, the excess reactant may be a gas, liquid, a semi-solid, solidparticle or a combination thereof. In the promotion of catalyticcracking, hydrogen and/or other light hydrocarbons may be very effectiveas an excess reactant. In an exemplary embodiment of the presentinvention, hydrogen may be injected with the additive (or as separatestreams) in the target reaction zone(s) (e.g. modified drill stem).Alternatively, compounds that release hydrogen (e.g. at highertemperatures) may be added to the coker feed (e.g. before or after thecoker feed heater). It is also anticipated that other chemical compoundsthat react with the target reactants to promote catalytic reactionmechanisms could be developed for these purposes, as well.

In the case of hydrogen and/or hydrogen generating compounds, gettingthe hydrogen to the primary reaction zone prior to reacting is a keyissue. In many cases, adding hydrogen to the additive package would becounterproductive, because the hydrogen would likely participate invapor overcracking in the upper part of the coke drum. For this reasonspecial options to add hydrogen separately from the additive need to beseriously considered. This is why several options are noted in FIG. 3and FIG. 4 for the injection of hydrogen into the coker feed eitherbefore or after the heater. This hydrogen is still likely to be consumedin reactions prior to reaching the target reaction zone (e.g. the liquidlayer) where it could enhance the catalytic reactions. In this case,compounds that generate hydrogen in the target area may be worthconsidering. However, the highest probability of getting hydrogen to thetarget reaction zones of the liquid and foam layers would be to injectit through a modified drill stem, similar to the one discussed in U.S.patent application Ser. No. 11/178,932 (i.e., U.S. Publication No.2006/0032788).

In the promotion of coke formation, various types of excess reactantsmay be used for this purpose. Ideally, the excess reactant would containvery high concentrations of chemical elements or chemical compounds thatreact directly with the heavy hydrocarbons in the liquid layer andvapors within the coking vessel. Availability or cost issues may makethe use of existing process streams with high aromatics contentdesirable, preferably over 50 weight percent aromatics. In addition, thecharacteristics of the excess reactant would preferably include (but notrequire), high boiling point materials, preferably greater than 800degrees Fahrenheit and high viscosity materials, preferably greater than5000 centipoise. Excess reactant(s) of choice may include carbon oraromatic organic compounds. However, in many cases, the practical choicefor excess reactant(s) would be decanted slurry oil from the refinery'sFluid Catalytic Cracking Unit (FCCU). In certain cases, the slurry oilmay still contain spent FCCU catalyst (i.e., not decanted). Also, slurryoil could be brought in from outside the refinery (e.g. nearbyrefinery). Other excess reactants would include, but should not belimited to, gas oils, extract from aromatic extraction units (e.g.phenol extraction unit in lube oil refineries), coker feed, bitumen,other aromatic oils, crushed coke, activated carbon, or combinationsthereof. These excess reactants may be further processed (e.g.distillation) to increase the concentration of desired excess reactantscomponents (e.g. aromatic compounds) and reduce the amount of excessreactant required and/or improve the reactivity, selectivity, oreffectiveness of excess reactants with the targeted heavy hydrocarbons.

The amount of excess reactant used will vary for each application,depending on various factors, including (but not limited to) the amountof catalyst, catalyst activity and selectivity, coke specifications andcost. In many applications, the quantity of excess reactant will besufficient to provide more than enough moles of reactant to coke allmoles of heavy hydrocarbons that are not cracked to more valuable liquidproducts. Preferably, the molar ratio of excess reactant to uncrackedheavy hydrocarbons would be 0.5:1 to 3:1. However, in some cases, littleor no excess reactant may be desirable in the additive. In many cases,the amount of excess reactant will be less than 15 weight percent of thecoker feed. Most preferably, the quantity of excess reactant would bebetween 0.05 weight percent of the coker feed input to 3.0 weightpercent of the coker feed input. For gaseous hydrogen, the quantityshould be in the range of about 30 to about 600 SCF per barrel of thecoker feed. As described, this excess reactant may be injected into thecoking vessel (e.g. above the vapor/liquid interface in the coke drumduring the coking cycle of the delayed coking process), the coker feed,and/or the transfer line between the heater and coke drum by variousmeans, including (but not limited to) pressurized injection with orwithout carrier fluid(s): gas oils hydrocarbon(s), oil(s), inorganicliquids, water, steam, nitrogen, hydrogen, or combinations thereof.

Carrier Fluid(s):

In general, a carrier fluid comprises any fluid that makes the additiveeasier to inject into the coking vessel. The carrier may be a liquid,gas, hydrocarbon vapor, or any combination thereof. The preferredcarrier fluid(s) for each application will often be determined byvarious factors, including (but not limited to) cost, refinery processscheme, proximity to the additive addition system, and carrier fluid(s)characteristics (e.g. boiling range, viscosity, density). In many cases,the carrier will be a fluid available at the coking process, such as gasoils, lighter liquid process streams, or even coker feed. In many cases,gas oil at the coking process is the preferable carrier fluid. However,preferred carrier fluid(s) may include process streams from otherprocess units at the refinery. In many cases, decanted slurry oil fromthe Fluid Catalytic Cracking Unit (FCCU) provides very good carrier oilcharacteristics (e.g. boiling range and high aromatic content), and manycokers already have this process stream previously piped up to thecoking process unit for coker feed additive to control coke morphology.Similarly, FCCU heavy Cycle Oil (HCO) and FCCU Light Cycle Oil (LCO)often provide good carrier oil characteristics, and is already piped tomany coker units for flush oil for seals on many pumps in the cokingprocess unit. In certain refineries other factors may make other carrierfluid(s) desirable. As such, carrier fluid(s) would include, but shouldnot be limited to, gas oils, other hydrocarbon(s), other oil(s),inorganic liquids, water, steam, nitrogen, or combinations thereof. Withall carrier fluid(s), additional quench agent(s) (described below) canbe added, as needed.

In an exemplary embodiment using a catalytic additive of the presentinvention, the Ideal′ carrier fluid(s) would primarily (1) protect theactivity of the catalyst until the catalyst reaches its targetedreactants (e.g. heavy hydrocarbons in the liquid layer, the foam layer,and product vapors). (2) limit exposure of active catalyst to high valueproduct vapors that could be catalytically cracked (i.e. catalyticovercracking) to low value fuel gas, (3) quench thermal vaporovercracking reactions as it evaporates to prevent the conversion ofvaluable ‘cracked liquids’ (e.g. gas oils, naphtha, etc.) in the productvapors to low value fuel gas, and (3) condense highest boiling pointcompounds in the product vapors (e.g. traditional coker recycle) as itevaporates onto the catalyst to create intimate contact between thecatalyst and these target heavy hydrocarbon reactants. With the intimatecontact with the catalyst, the condensed coker recycle components willlikely crack to smaller molecules that have sufficiently high vaporpressure to escape the coke drum, even at lower coke drum outlettemperatures. The evaporation of these reaction products may cause alocalized temperature drop that condenses the highest boiling pointcompounds in the product vapors (e.g. traditional coker recycle)creating intimate contact with the catalyst. Ideally, this process(condensation, cracking reaction, evaporation, condensation, crackingreaction, evaporation, etc.) will be repeated many times as the catalystsettles to the foam/liquid layers. As such, the ‘ideal’ carrier fluid(s)may assist in these processes, to the extent possible, and optimize thefunctions described above.

With experience over time, for a given application, one skilled in theart is anticipated to be able to create the ‘ideal’ carrier fluid(s) inthe coker unit, elsewhere in the refinery, outside the refinery or anycombination thereof. That is, the ‘ideal’ carrier fluid(s) for a givenapplication may actually be created in the refinery in various processunits or the combining of different refinery process streams. Forexample, an ‘ideal’ carrier oil for an exemplary embodiment of thepresent invention may have a boiling range of 800 to 830 degreesFahrenheit from the coker fractionator or otherfractionator/distillation towers in nearby process unit. In many cases,this carrier oil would provide high coverage of the active catalystsites until it evaporated as the catalyst settled toward the liquid/foamlayers, where temperatures typically exceed 830° F. However, thiscarrier oil would have less vaporization in the upper coke drum toquench the vapor overcracking and cause less condensation of internalrecycle of the heavy recycle materials. Another alternative may be the‘extra heavy coker gas oil’ produced by a technology that has extrafractionator trays and a separate draw for traditional recyclecomponents or the heaviest components of the heavy coker gas oil (HCGO).Similarly, an extra product draw-off could be added to the vacuumdistillation column that would provide a carrier oil with a boilingrange of 800 to 830 degrees Fahrenheit. The use of a condensed liquidfrom the vapor line between the coke drums and the fractionator may alsoprovide an ‘ideal’ carrier oil that contains primarily traditional cokerrecycle material, along with some condensed vapor line quench oil. Thistype of carrier oil could provide the protection of the catalyst fromcoke drum vapors, while creating intimate contact between a targetreactant and the catalyst with a lower quench level than other carrieroils. Other examples of the production and use of the ‘Ideal CarrierOil’ may include (but should not be limited to) the use of crude oiland/or coker feed, alone or combined with other process streams. Theseexamples of ‘ideal carrier oils’ may be appropriate for limitedapplications.

The amount of carrier fluid(s) used will vary for each application,depending on various factors, including (but not limited to) the amountof catalyst, catalyst activity and selectivity, coker processlimitations, coke specifications, and cost. In many applications, littleor no carrier is actually required, but desirable to make it morepractical or cost effective to inject the additive into the cokingvessel. The quantity of carrier fluid(s) will be sufficient to improvethe ability to pressurize the additive for injection via pump orotherwise. In many cases, the amount of excess reactant will be lessthan 15 weight percent of the coker feed. Most preferably, the quantityof carrier fluid would be between 0.5 weight percent of the coker feedinput to 3.0 weight percent of the coker feed input. As described, thiscarrier may help injection of the additive into the coking vessel (e.g.above the vapor/liquid interface in the coke drum during the cokingcycle of the delayed coking process) by various means, including (butnot limited to) pressurized injection with or without carrier fluid(s):gas oils hydrocarbon(s), oil(s), inorganic liquids, water, steam,nitrogen, or combinations thereof.

Quenching Agent(s):

In general, a quenching agent comprises any fluid that has a net effectof further reducing the temperature of the product vapors in the cokingvessel. The quenching agent(s) may be a liquid, gas, hydrocarbon vapor,or any combination thereof. Many refinery coking processes use a quenchin the vapors downstream of the coking vessel (e.g. coke drum). In somecases, this quench may be moved forward into the coking vessel. In manycases, a commensurate reduction of the downstream quench may bedesirable to maintain the same heat balance in the coking process. Inmany cases, gas oil available at the coking process will be thepreferred quench. However, quenching agents would include, but shouldnot be limited to, gas oils, FCCU slurry oils, FCCU cycle oils, otherhydrocarbon(s), other oil(s), inorganic liquids, water, steam, nitrogen,or combinations thereof.

The amount of quench used will vary for each application, depending onvarious factors, including (but not limited to) the temperature of thevapors in the coking vessel, the desired temperature of the vaporsexiting the coking vessel, and the quenching effect of the additivewithout quench, characteristics and costs of available quench options.In many applications, the quantity of quench will be sufficient tofinish quenching the vapors from the primary cracking and coking zone(s)in the coking vessel to the desired temperature. In some cases, littleor no quench may be desirable in the additive. In many cases, the amountof quench will be less than 15 weight percent of the coker feed. Mostpreferably, the quantity of quench would be between 0.5 weight percentof the coker feed input to 3.0 weight percent of the coker feed input.As described, this quench may be injected into the coking vessel (e.g.above the vapor/liquid interface in the coke drum during the cokingcycle of the delayed coking process) as part of the additive by variousmeans, including (but not limited to) pressurized injection with orwithout carrier fluid(s): gas oils hydrocarbon(s), oil(s), inorganicliquids, water, steam, nitrogen, or combinations thereof. This quenchmay also be added to the coking vessel separately from the additive.

Additive Combination and Injection:

In an exemplary embodiment of the present invention, an additive mixingsystem would be used to properly mix the additive components to thedesired concentrations and blend consistency. The additive mixing systemwould combine the 5 components to the degree determined to be desirablein each application (e.g. some components may not be used in aparticular application of the additive blend). In many cases, all of theadditive components would be blended by mixing device(s), preferably toa homogeneous consistency, and heated to the desired temperature (e.g.heated, mixing tank) by a temperature regulation system. For example,the desired temperature (>150 degrees Fahrenheit) of the mixture mayneed to be increased to maintain a level of viscosity for proper pumpingcharacteristics and fluid nozzle atomization characteristics. Theadditive mixing system can be continuous, batch, periodic, intermittent(e.g. middle of coking cycle only), other operational basis, or anycombination thereof. In some applications, certain additive componentsmay be injected separately. In other applications, the additiveformulation (e.g. component concentrations) may not be constant and maychange throughout the coking cycle or injection period.

In an exemplary embodiment of the present invention, the additiveaddition system will effectively use measurement device(s) andcontrol(s) to maintain the appropriate profiles throughout the additionsystem for temperature, pressure, and flow rates. The mixed additive, atthe desired temperature and pressure, would be pressurized (e.g. viapump or pressurized fluid) to a pressure level sufficiently higher thanthe coking vessel operating pressure to allow for the proper pressuredrop across the piping and atomizing nozzle to achieve the desired flowand spray characteristics. At the desired operating pressure, the mixedadditive may be injected (e.g. via atomizing injection nozzle) into thecoking vessel at the desired level above the primary cracking and cokingzones. The additive addition system may be continuous, intermittent,periodic (e.g. middle of coking cycle only), batch injection (all atonce per coking cycle), other operational basis, or any combinationthereof. The injection points into the coking vessel can vary fromcoking unit to coking unit, due to site specific factors, including (butnot limited to) (1) current coke drum design and operation, (2) cokingvessel mechanical configuration, (3) additive addition system design andoperation, and (4) piping distance (e.g. pipe rack path) from additiveaddition system to the coking vessel. In many cases, insulated pipingwill be desirable to keep the additive at the desired temperature. Incertain applications, heat tracing or steam jacketing of pipes may benecessary to maintain the desired temperature from the addition systemto the coking vessel. Also, injection nozzles (though not required) willbe desirable in many cases to evenly distribute the additive across thecross sectional profile of the product vapor stream in the cokingvessel. The injection nozzles should also be designed to provide theproper droplet size (e.g. 50 to 150 microns) to prevent entrainment ofnon-vaporized components (e.g. catalyst) in the vapor product gases,exiting the top of the coking vessel (e.g. coke drum). Typically, theseinjection nozzles would be aimed countercurrent to the flow of theproduct vapors. The injection velocity should be sufficient to penetratethe vapors and avoid direct entrainment into the product vapor stream.However, the injection nozzles design and metallurgy must take intoaccount the potential for plugging and erosion from the solids (e.g.catalyst) in the additive package, since the sizing of such solids mustbe sufficient to avoid entrainment in the product vapor stream.Furthermore, the additive addition system can be set up to providecontinuous injection, intermittent injection, periodic injection (e.g.middle of coking cycle only), batch injection (all at once per cokingcycle), other operational basis, or any combination thereof. Finally,the additive addition system in an exemplary embodiment of the presentinvention may require additional measurement device(s) and controldevice(s) to coordinate the injection of two or more additive streams,and/or the use of two or more additive mixing/addition systems.

In another embodiment, said additive components can be added to thecoker product vapors in separate process streams. For example, thecatalyst can be added separately from a quench agent to selectivelycondense the highest boiling components in the product vapors. Thecarrier fluid(s) in said additive may no longer carry other additivecomponents, but may simply become quench oil. This may be preferable inapplications (1) where the catalyst is more easily injected in a dryform and/or (2) where a catalyst of a higher temperature is desirable.In this example, the coincidental injection of both the quench agent(s)and the catalyst(s) near the same location may be desirable in a mannerthat enhances the intimate contact of the catalyst and condensed highestboiling point components of the coker product vapors to increaseselectivity of the desired reactions. In another example, hydrogen maybe added as a separate process stream, as well. That is, the addition ofhydrogen as a separate process stream may be preferable, whether theremaining additive is injected in one process stream or multiple processstreams.

In another exemplary embodiment of the present invention, a separateaddition of colder catalyst may also be desirable in certainapplications. The colder catalyst may be sufficient to condense thehighest boiling materials in the product gases to achieve a desiredintimate contact with the coke (e.g. selective reaction with catalyst),but the drop in temperature would not normally be sufficient to condensea higher level of the highest boiling materials due to the lack ofsubstantial heat loss from the heat of vaporization in a carrier/quenchoil.

In another embodiment of the present invention, the addition of saidadditive into the vapor line (line 38 in FIGS. 2 & 3) between coke drumand the coker fractionator (downstream of the coke drum and preferablyas close to the coke drum outlet as possible) may be desirable in someapplications of the technology. Though this embodiment would not havethe benefit of higher temperatures in the coking vessel and/or highertemperatures associated with the reheat of the internal recycle (e.g. asthe catalyst/condensed coker product vapors sink to the liquid cokinglayer in the coke drum), some enhanced chemical reactions may stillprovide sufficient benefits to justify its application. For example,said additive in the form of heated catalyst(s) could be injected intothe vapor line and achieve some desired benefits. In this case, quenchoil injection in said vapor line may already exist in the coker of saidapplication to condense the highest boiling components of the cokerproduct vapors. In addition, some applications may already haveparticulate collection devices near the inlet to the coker fractionator(e.g. before the coker product vapors entrance to the cokerfractionator) to collect coke particles. These existing particulatecollection device(s) may be sufficient to collect additionalparticulates from (1) solid components of said additive (e.g. catalyst)or (2) solid derivatives from reactions caused by injection of saidadditive. Otherwise, the particulate collection devices may be modifiedand/or new collection devices added to handle the additional particulateloading and different particle characteristics. This is typically not apreferred embodiment due to the potential lower temperatures in thevapor line (e.g. less effective use of the catalyst) and the potentialproblems associated with catalyst (if used) or seeding agents (if used)getting into the fractionator (and coker product streams) or beingrecycled through the process heater (with associated fouling).

In another exemplary embodiment of the present invention, part of thesaid additive could be introduced in the transfer line (see 218 in FIGS.2 & 3) between the heater and the coke drum (upstream of the coke drum)to enhance the catalytic reactions in the coking vessel. This embodimentwould likely encounter similar problems with catalyst(s) being injectedin the coker feed prior to the process heater (i.e. catalyst and othermaterials act as seeding agent that promotes more coke formation, notless) and would not be as effective use of the catalyst. As such,additional catalyst may be necessary to achieve desired levels. However,this embodiment may be desirable in certain applications (e.g. low cokedrum temperatures less than 890 degrees Fahrenheit). The temperature ofthe multi-phase material in this transfer line is typically between 890and 930 degrees Fahrenheit. As such, the addition of sufficientcatalytic additive in the transfer line may reduce the temperature dropin the transfer line (and maintain higher coke drum temperatures) due tolower energy required by catalyst(s) for similar endothermic crackingreactions (same reactants and same products) that take place in thetransfer line. Furthermore, all of said additive could be added in thetransfer line in certain applications (e.g. coke drum temperature is toolow in the coke drum due to coker feed significantly below designrates). As described previously, the additive in this embodiment may beinjected in the transfer line (see 218 in FIGS. 2 & 3). In this manner,addition of additive in the transfer line in combination with additionof additive above the liquid/foam layer interface may provide enhancedbenefits.

In another embodiment, said additive of the present invention could alsobe added by various mechanical system(s) to the foaming and/or liquidlayers below the product vapors of the delayed coker. These mechanicalsystem(s) of adding said additive could be continuous injection,intermittent or periodic injection (e.g. middle of coking cycle only),batch injection (all at once per coking cycle), or any combinationthereof. One exemplary mechanical system to achieve this may be amodified drill stem, as shown in FIG. 4. As discussed previously, drillstems (similar to those used for decoking the coke from the coke drumduring the decoking cycle of the delayed coking process) may be modifiedin design to deliver the additive (e.g. hot catalyst only) directly tothe foam/liquid layers of the coking cycle. That is, the modified drillstem would lead the rising foam/liquid layers and add the additive tothe foam/liquid layers with very limited exposure of the additive to theproduct vapors above the foam/liquid layers in the coke drum during thecoking cycle. In this manner, the catalyst is less likely to cause vaporovercracking of the product vapors, and carrier fluid(s) and/or quenchagents(s) (and their associated limitations) become less desirable. Ifthe status of current technologies (e.g. high-pressure drum sealingtechnology, metallurgy of components, etc.) are not prohibitive at thecurrent time, the use of the modified drill stem, which can safely andreliably follow the upward movement of the foaming and/or liquid layersthroughout the coking cycle, would provide a preferred embodiment tointroduce active catalyst into the foaming and/or liquid layers. Theintroduction of hydrogen and/or hydrogen releasing compounds in theadditive and/or a separate stream vis the modified drill stem would alsobe preferable. Drill stem(s) may be provided to satisfy this additive(s)injection service and the decoking service for which it was originallydesigned.

The additive package of an exemplary embodiment of the present inventionmay also include anti-foam solution that is used by many refiners toavoid foamovers. These antifoam solutions are high density chemicalsthat typically contain siloxanes to help break up the foam at thevapor/liquid interface by its affect on the surface tension of thebubbles. In many cases, the additive package of an exemplary embodimentof the present invention may provide some of the same characteristics asthe antifoam solution; significantly reducing the need for separateantifoam. In addition, the existing antifoam system may no longer benecessary in the long term, but may be modified for commercial trials ofan exemplary embodiment of the present invention. In an exemplaryembodiment of the present invention, the additive may have substantialanti-foam characteristics on its own and may act as a suitablereplacement of traditional anti-foams used in delayed cokerapplications. In other applications the combination of the additive andtraditional anti-foams may be very effective. Among other reasons, theadditive of the present invention may act as a carrier for thetraditional anti-foams to carry anti-foam to the foam and liquid surface(vs. going out the drum outlet with product vapor entrainment). Inaddition, other, more desirable anti-foams may be developed to becombined with the additive to provide a more cost effective solution.

Theory of Operation: Said additive of the present invention is believedto selectively convert the highest boiling point materials in theproduct vapors of the coking process by (1) condensing vapors of saidhighest boiling point materials and increasing the residence time ofthese chemical compounds in the coking vessel, (2) providing a catalystto reduce the activation energy of cracking for condensed vapors thathave a higher propensity to crack (vs. coke), and (3) providing acatalyst and excess reactant to promote the coking of these materialsthat have a higher propensity to coking (vs. cracking). That is, thelocalized quench effect of the additive would cause the highest boilingpoint components (e.g. heavy hydrocarbons) in the product vapors tocondense on the catalyst and/or seeding agent, and cause selectiveexposure of the heavy hydrocarbons to the catalysts' active sites. Ifthe heavy hydrocarbons have a higher propensity to crack, selectivecracking will occur, the cracked liquids of lower boiling point willvaporize and leave the catalyst active site. This vaporization causesanother localized cooling effect that condenses the next highest boilingpoint component. Conceivably, this repetitive process continues untilthe catalyst reaches the liquid/foam layers of the coking vessel. In theliquid/foam layers, the catalyst would continue to promote catalyticcracking of heavy hydrocarbons until its active sites encounter acondensed component that has a higher propensity to coke (vs. crack) inthe particular coking vessel's operating conditions or the coking cycleends. Equilibrium for the catalytic cracking (vs. coking) of heavyaromatics has been shown to favor lower temperatures (e.g. 800 to 850°F. vs. 875 to 925° F.), if given sufficient residence time and optimalcatalyst porosity and activity levels. The additive settling time andthe time at or below the vapor/liquid interface provide much longerresidence times than encountered in other catalytic cracking units (e.g.FCCU). Thus, the ability to crack heavy aromatics is enhanced by thismethod of catalytic cracking. Ideally, the additive's active sites inmany applications would crack many molecules of heavy hydrocarbons,prior to and after reaching the vapor/liquid interface, beforeselectively coking heavy aromatic components and being integrated intothe petroleum coke. This invention should not be limited by this theoryof operation. However, both the injection of this type of additivepackage and the selective cracking and coking of heavy aromatics arecontrary to conventional wisdom and current trends in the petroleumcoking processes.

Enhancement of Additive Effectiveness:

It has also been discovered that minor changes in coking processoperating conditions may enhance the effectiveness of the additivepackage. The changes in coker operating conditions include, but shouldnot be limited to, (1) reducing the coking vessel outlet temperature,(2) increasing the coking vessel outlet pressure, (3) reducing thecoking feed heater outlet temperature, or (4) any combination thereof.The first two operational changes represent additional means to condensethe highest boiling point materials in the product vapors to increasetheir residence time in the coking vessel. In many cases, the additivepackage is already lowering the temperature of the product vapors by itsquenching effect and the intentional inclusion of a quenching agent inthe additive package to increase this quenching effect. However, manycoking units have a substantial quench of the product vapors in thevapor line between the coking vessel and the fractionator to preventcoking of these lines. In many cases, it may be desirable to move someof this quench upstream into the coking vessel. In some coking units,this may be accomplished by simply changing the direction of the quenchspray nozzle (e.g. countercurrent versus cocurrent). As notedpreviously, a commensurate reduction in the downstream vapor quenchingis often desirable to maintain the same overall heat balance in thecoking process unit. If the coking unit is not pressure (compressor)limited, slightly increasing the coking vessel pressure may bepreferable in many cases due to less vapor loading (caused by thequenching effect) to the fractionator and its associated problems.Finally, slight reductions of the feed heater outlet temperature may bedesirable in some cases to optimize the use of the additive in exemplaryembodiments of the present invention. In some cases, reduction of thecracking of heavy aromatics and asphaltenes to these ‘heavy tail’components may reduce the amount of additive required to remove the‘heavy tail’ and improve its effectiveness in changing coke morphologyfrom shot coke to sponge coke crystalline structure. In some cases,other operational changes in the coking process may be desirable toimprove the effectiveness of some exemplary embodiments of the presentinvention.

In the practical application of an exemplary embodiment of the presentinvention, the optimal combination of methods and embodiments will varysignificantly. That is, site-specific, design and operational parametersof the particular coking process and refinery must be properlyconsidered. These factors include (but should not be limited to) cokerdesign, coker feedstocks, coker operating conditions (e.g. temperatureand pressure profiles in the coking vessel) and effects of otherrefinery operations.

Use of Additive to Increase Selectivity of Additive Components:

It has been discovered that an additive may be introduced into thevapors of coking vessel of traditional coking processes to condense thevapors of highest boiling point compounds and facilitate contact withcomponents of the additive. Intimate contact of the highest boilingpoint compounds with catalyst(s), seeding agent(s), excess reactant(s),or any combination of these components contained in the additive willfacilitate selective conversion of these highest boiling point compoundsof the product vapors. In effect, this condensation mechanism wouldreduce the amount of the highest boiling point materials in the productvapors from the primary cracking and coking reaction zone(s), whichwould otherwise pass through as recycle to the coking process heater(potentially reducing coking process capacity) and/or to thefractionation portion of the coking process as the ‘heavy tail’ of theheavy coker gas oil, which potentially reduces the catalyst activity andcauses operational problems in downstream catalytic cracking units.

In this discussion and throughout this application, the term ‘highestboiling point compound’ recognizes that the order of boiling points ofthe condensed compounds or the coking vessel operating temperature atwhich these compounds condense will not necessarily follow in strictnumerical order (e.g. 830 degrees Fahrenheit, 829 degrees Fahrenheit,828 degrees Fahrenheit, etc.). In practical application, thedistribution of additive may not be uniform, causing localized heatconditions that are not uniformly distributed in the vapor space of thecoking vessel. Other heat distribution factors will also come into play,as well. Thus, some of the condensed vapors in the coking vessel mayactually have lower boiling points than some of the vapors that do notcondense, and remain vapors.

In one exemplary embodiment of the present invention, the quenchingeffect of the additive can be used to condense the highest boiling pointcompounds of the product vapors onto the catalyst(s) in the additive,thereby improving the catalyst selectivity. That is, the additive canfocus the catalysts exposure to the highest boiling point compounds inthe product vapors. With a properly designed catalyst to crack thesehighest boiling point materials, this mechanism can effectively increasethe catalyst's selectivity, thereby increasing its efficiency andreducing catalyst requirements and costs.

In another exemplary embodiment of the present invention, the contact ofhighest boiling point compounds of the product vapors with catalyst(s),seeding agent(s), excess reactant(s), or any combination of thesecomponents of the additive can facilitate selective conversion of thesehighest boiling point compounds. The selective conversion could includecatalytic cracking, catalytic coking, thermal cracking, thermal coking,or any combination of these reactions. In some cases, selective cokingof these highest boiling point materials to an optimal extent canimprove the coke quality sufficiently to leverage the total value of thecoke over the lost value of these materials that can reduce cokercapacity or cause operating problems and loss of efficiency indownstream processing units. In other cases, maximizing or optimizingcoke production may be desirable, such as needle coke or anode cokeproduction facilities.

By condensing these highest boiling point materials of the productvapors, exemplary embodiments of the present invention can essentiallycreate an ‘internal recycle’ that increases the residence time of theheaviest components of the coker recycle and/or part of the HCGO. Inaddition, this ‘internal recycle’ may also be used to provide intimatecontact with the catalyst and make it more selective and efficient,thereby lowering catalyst requirements and costs. However, the catalystmust be designed to effectively crack these very large molecules in theliquid phase, or crack in the gas phase after the catalyst settles to alevel in the coking vessel where these highest boiling point materialsrevaporize due to the higher temperatures or other local sources of heat(e.g. release of heat from condensation of adjacent molecules). Thequantity of ‘internal recycle’ depends on various factors, including (1)the coking vessel outlet temperature of the known art, (2) the quantityof catalytic additive and its associated quenching effect, and (3) thequality and quantity of coker recycle and Heavy Coker Gas Oil.

In exemplary embodiments of the present invention, catalytic cracking ofthe highest boiling point materials in the product vapors of the cokingvessel may allow one skilled in the known art to reduce the quantity oftraditional coker recycle (i.e. external) and/or reduce the amount of‘heavy tail’ components in the HCGO. Where the reduction shows up can beoptimized by adjusting the end point of the HCGO in the fractionatoroperation.

This additive selectively removes these highest boiling components fromthe product vapors in a manner that encourages further conversion (e.g.,cracking or coking) of these materials in the coking vessel. Minorchanges in coking process operating conditions may enhance theeffectiveness of the additive package. The amount of highest boilingpoint materials that are converted in this manner is dependent on (1)the quality and quantity of the additive package, (2) the existingdesign and operating conditions of the particular coking process, (3)the types and degree of changes in the coking process operatingconditions, and (4) the coking process feed characteristics.

Typically, these highest boiling point materials in the product vaporshave the highest molecular weight, have a propensity to coke, and arecomprised primarily of heavy hydrocarbons with boiling points exceeding700° F. These heavy hydrocarbons typically come from the thermalcracking of asphaltenes, resins, and other aromatics in the coker feed.The highest boiling point materials have traditionally ended up in thecoker recycle, where it often would coke in the heater or possibly cracksome additional side chains. However, with minimal recycle rates toincrease coker capacities, many of these materials are destined to bethe highest boiling components of the heavy coker gas oil, though somemany will still end up in be in the coker recycle. That is, the splitbetween heavy coker gas oil and recycle will depend on the quantity ofrecycle, which are essentially these materials. As such, the cokeroperator may modify the coker operation to affect the fate of thesehighest boiling components: recycle vs. ‘heavy tail’ of the heavy cokergas oil. (For simplicity, the highest boiling materials in the productvapors may be referred to as gas oil ‘heavy tail’ components throughoutthe remaining discussion, even though some of these materials may gointo the coker recycle stream). Furthermore, many other coking processtechnology improvements have increased the quantity and boiling pointsof these materials in the gas oil and substantially decreased thequality of the gas oils that are further processed in downstreamcatalytic cracking units. That is, the heaviest or highest boilingcomponents of the coker gas oils (often referred to as the ‘heavy tail’in the art) are greatly increased in many of these refineries(particularly with heavier, sour crudes). These increased ‘heavy tail’gas oil components cause significant reductions in the efficiencies ofdownstream catalytic cracking units. In many cases, these ‘heavy tail’components contain much of the remaining, undesirable contaminants ofsulfur, nitrogen, and metals. In downstream catalytic units, theseadditional ‘heavy tail’ components tend to significantly deactivatecracking catalysts by increasing coke on catalyst and/or poisoning ofcatalysts via blockage or occupation of active sites. In addition, theseproblematic ‘heavy tail’ components of coker gas oils also may increasecontaminants in downstream product pools, consume capacities of refineryammonia recovery and sulfur plants, and increase FCCU catalystattrition, catalyst make-up rates, and environmental emissions.

Selective, catalytic conversion of the highest boiling point materialsin the coking process product vapors (coker recycle and/or ‘heavy tail’of the heavy coker gas oil) may be accomplished with exemplaryembodiments of the present invention in varying degrees. The selectiveconversion of these heavy hydrocarbon components may be optimized in anexemplary embodiment of the present invention by (1) proper design andquantity of the additive package and (2) enhancement via changes in thecoking process operating conditions.

Description of Additive Reactants:

Exemplary embodiments of the present invention generally introduce acatalytic additive into the coking vessel of the coking process at orabove the vapor/liquid interface or, alternatively, at or above thecoking interface (i.e. the coke/liquid interface). In this manner, theprimary reactants exposed to the catalyst in exemplary embodiments ofthe present invention are (1) the vapor products resulting from thethermal cracking and thermal coking of the coker feed and (2)essentially coker feed derivatives (also from thermal cracking andthermal coking) in the liquid, emulsion, and foam layers (below thevapor/liquid interface), after the catalyst has settled there. As such,the primary catalytic reactants in exemplary embodiments of the presentinvention have substantially different chemical and physicalcharacteristics than the reactants of the known art, wherein catalyst isadded to the coker feed of the coking process.

The hydrocarbon feed of the coking process is typically a residuumprocess stream (e.g. vacuum tower bottoms), comprised of very heavyaromatics (e.g. asphaltenes, resins, etc.) that have theoretical boilingpoints greater than 1050 degrees Fahrenheit. Typical ranges (Wt. %) ofSARA for the coker feed components are as follows: 1-10% Saturates,10-50% Aromatics, 30-60% Resins, and 15-40% Asphaltenes. As such, theprimary reactants exposed to the catalysts of the known art are heavyaromatics with a substantially higher propensity to coke, particularlywith the exposure to high vanadium and nickel content in the coker feed.Furthermore, mineral matter in the coker feed tends to act as a seedingagent that further promotes coking. Calcium, sodium, and ironcompounds/particles in the coker feed have been known to increasecoking, particularly in the coker feed heater. Similarly, the catalystmay act as a seeding agent, as well.

From a physical perspective, the primary reactants of the known art(i.e. catalyst in the feed) are a very viscous liquid (some partssemi-solid) at the inlet to the coker feed heater. Throughout the heaterand into the coke drums the feed becomes primarily hot liquid, somesolids (from feed minerals and coking), and vapors (e.g. from coker feedcracking). The temperature of the multi-phase material at the inlet tothe drum is typically between 900 and 950 degrees Fahrenheit.

In contrast, the catalyst reactants in an exemplary embodiment of thepresent invention are primarily derivatives (or partially crackedportions) of the coker feed. That is, the reactants that are exposed tothe catalyst additive in exemplary embodiments of the present inventionare mostly the products of the thermal cracking and thermal coking ofthe coker feed. The catalyst additive of the exemplary embodiments ofthe present invention have very limited exposure to coking process feedcomponents, when the catalyst settles to the liquids above the cokinginterface (e.g. coke/liquid interface) and becomes part of the solidcoke. Even here, most of the coker feed has been converted to smallercompounds with lower propensity to coke (vs. coking process feed). Thus,reactants exposed to the catalyst additive of the present invention aresubstantially more likely to crack than the components of the coker feedthat are exposed to catalysts introduced into the coking process feed inthe known art.

The product vapors at or above the vapor/liquid interface in the cokingvessel comprise various derivatives of the coker feed components, thatare thermally cracked upstream of this point in the coking vessel. Inthe known art, these product vapors continue to thermally crack untilthey exit the coking vessel, where they are typically quenched in thevapor line to stop coking and cracking reactions. After fractionation,these product vapors (many condensed) are normally classified by boilingpoint range into the following groups: gas (less than 90 degreesFahrenheit), light naphtha (roughly 90 to 190 degrees Fahrenheit), heavynaphtha (roughly 190 to 330 degrees Fahrenheit), Light Coker GasOil—LCGO (roughly 330 to 610 degrees Fahrenheit), Heavy Coker GasOil—HCGO (roughly 610 to 800 degrees Fahrenheit), and coker recycle(greater than roughly 800 degrees Fahrenheit). The vapor products in thecoking vessel can be thought of as having the same boiling pointclassifications at any point in time that it is exposed to a catalyticadditive of the present invention. However, the vapor products arerecognized to have higher proportions of heavier products than whatcomes from the fractionator due to further thermal cracking in thevapors prior to the vapor line quench and the fractionator. In otherwords, the further upstream from the fractionator, the higher theproportions of heavier products.

Below the vapor/liquid interface (down to the coking interface andbelow), the solids, liquids, and vapors comprise mostly chemicalcompounds of converted coker feed components. As the catalyst in anexemplary embodiment of the present invention settles into the foam andliquid layers, it may be exposed to these solids, liquids and vapors. Inmany cases, the solid portions represent coke from thermal coking of thecoker feed components. The liquid and some semi-solid portions in theselayers may contain components of the coker feed, but many of the liquidsare likely derivatives (or cracked) components of the coker feed at thispoint, particularly toward the end of the coking cycle. At this level,the vapors emerging from the coking interface are essentially crackedcoker feed components, derivatives of the heavier saturates, aromatics,resins, and asphaltenes in the coking process feed that have theoreticalboiling points greater than 1050 degrees Fahrenheit. Conceivably, thecatalyst of exemplary embodiments of the present invention can stillfacilitate cracking and coking reactions, even as the catalyst becomespart of the coke layer. At this level, the catalyst is still exposedprimarily to derivatives of the coker feed: coke and vapor/liquidspassing through the coke layer. In conclusion, even after settling tothe vapor/liquid interface and below, the catalyst in exemplaryembodiments of the present invention can still facilitate cracking andcoking reactions (inherent aspects of the present invention). Even atthese levels, the overall exposure of the catalyst to coker feedcomponents with a higher propensity to coke is limited.

In the known art of the refining industry, the product classificationshave broader classification of low boiling point, middle boiling point,and high boiling point materials or products. Typically, theclassification of low boiling point products comprises the chemicalcompounds that are in the gas phase at ambient temperatures andpressures, including methane, ethane, propanes, butanes, and thecorresponding olefins. These compounds typically have boiling pointsless than roughly 90 degrees Fahrenheit, and are commonly referred to asC4—in the industry, referring to the number of carbon atoms in eachmolecule. The middle boiling point products are typically liquids atambient temperatures and pressures, and boiling points between roughly90 and 610 degrees Fahrenheit. Most of these middle boiling pointproducts, including middle distillates, are blended into liquidtransportation fuels either directly or after further processing (e.g.hydrotreating, reforming, isomerization) to improve product qualities.Typically, high boiling point materials are considered to be refineryprocess streams with boiling point ranges greater than the middledistillates. These process streams normally require further processing(e.g. hydrocracker or fluid catalytic cracking unit) to lower theirboiling point range before they can be blended into liquidtransportation fuels. Generally, these materials have boiling pointsgreater than the highest end point of the middle distillates; typicallythe end point of light gas oils or approximately 610 degrees Fahrenheit.

Applying this known art to a coking process, the coker recycle and HeavyCoker Gas Oil (HCGO) would be classified as ‘high boiling pointmaterials’ in the product vapors in the coking vessel. As discussed inother parts of this description, some exemplary embodiments of thepresent invention can use the catalytic additive in to quench the vaporproducts and condense the ‘highest boiling point’ materials in theproduct vapors. By condensing these highest boiling point materials,exemplary embodiments of the present invention can essentially create an‘internal recycle’ that increases the residence time of the heaviestcomponents of the coker recycle and/or part of the HCGO. In addition,this ‘internal recycle’ may also be used to provide intimate contactwith the catalyst and make it more selective and efficient, therebylowering catalyst makeup requirements and costs. However, the catalystmust be designed to crack effectively with these very large molecules inthe liquid phase, until the catalyst settles to a level in the cokingvessel where these highest boiling point materials revaporize due to thehigher temperatures or other local sources of heat (e.g. release of heatfrom condensation of adjacent molecules). The quantity of ‘internalrecycle’ depends on various factors, including (1) the coking vesseloutlet temperature of the known art, (2) the quantity of catalyticadditive and its associated quenching effect, and (3) the quality andquantity of coker recycle and Heavy Coker Gas Oil. In exemplaryembodiments of the present invention, catalytic cracking of the highestboiling point materials in the product vapors of the coking vessel mayallow one skilled in the known art to reduce the quantity of traditionalcoker recycle (i.e. external) and/or reduce the amount of ‘heavy tail’components in the HCGO. Where the reduction shows up can be optimized byadjusting the end point of the HCGO in the fractionator operation.

From a physical perspective, the primary catalytic reactants of thepresent invention are primarily vapors, condensed liquids of the highestboiling point vapors, and liquids, semi-solids and solids at the cokinginterface (after the catalyst settles to the vapor/liquid interface andbelow). The temperature of the primary reactants is typically <875° F.,which is normally more conducive to aromatic cracking (vs. coking) withhigh residence time and reaction equilibrium, favoring these lowertemperatures. Physically, the primary catalytic reactants of exemplaryembodiments of the present invention are substantially different fromthe primary catalytic reactants of the known art and much less conduciveto coking.

In summary, the chemical and physical characteristics of the catalystreactants are vastly different for an exemplary embodiment of thepresent invention, when compared to the chemical characteristics of thecatalytic reactants of the known art. That is, the catalyst additive ofan exemplary embodiment of the present invention is typically added tothe coking vessel downstream of the primary cracking and coking zones ofthe coking process. In these cases, the primary reactants arederivatives of the coker feed after extensive cracking and coking of thecoker feed: coker recycle, heavy coker gas oil (HCGO), light coker gasoil (LCGO), naphtha, and various gases with less than 5 carbon atoms permolecule. The highest boiling point materials (e.g. greater than roughly800 degrees Fahrenheit) in the coker product vapors are the cokerrecycle and the ‘heavy tail’ of the heavy coker gas oil. Consequently,the primary reactants exposed to the catalyst of an exemplary embodimentof the present invention are substantially smaller molecules that aremore conducive to cracking (vs. coking) than the known art. Chemically,the primary catalytic reactants of an exemplary embodiment of thepresent invention are substantially different and much less conducive tocoking than the primary catalytic reactants of the known art.

The physical and chemical characteristics of the primary reactants inthe present invention are more similar to those in a fluid catalyticcracking unit (FCCU). That is, a typical FCCU further processes the HCGOgenerated by the coking process. The FCCU is typically used to convert(catalytically crack) the high boiling point materials (e.g. greaterthan roughly 610 degrees Fahrenheit) of the HCGO in a similar operatingenvironment with low pressure, limited hydrogen, and slightly highertemperatures. However, the substantially longer residence time for thecatalyst in exemplary embodiments of the present invention (potentiallyhours vs. seconds) is advantageous in achieving efficient use of thecatalyst with reaction kinetics that may more closely approachequilibrium values.

Hydrogen Addition Embodiment

An advantage of an exemplary embodiment of the present invention is toget active catalyst of desired characteristics down to theliquid/emulsion and foaming layers above the coke to convert heavierhydrocarbons (that would otherwise form coke) to lighter hydrocarbonswith high enough vapor pressure (low enough boiling point) to escape thecoke drum (even at lower coke drum outlet temperatures), and beseparated into process streams in the coker fractionator.

The thermal and catalytic cracking vapor/liquid equilibria for variousreactions of the present invention at various temperatures at the top ofthe coke drum are more favorable than the thermal cracking vapor/liquidequilibria of traditional delayed coking at various temperatures at thetop of the coke drum. Part of this has to do with many of the reactionsare reaction rate limited, and/or the concentration of the desiredreactants are increased by removing an excess of chemical compounds fromthe reaction zone that don't react in the traditional delayed cokingenvironment. Though the delayed coker reaches a somewhat steady stateoperation the reaction kinetics are still dynamic (not at equilibrium).However, these reaction equilibria driving forces for various reactionspush the coker product yields more favorably toward the Technology at agiven coke drum vapor exit temperature.

Catalyst can be fluidized for extended periods of time due to turbulentmix zones in the liquid/emulsion and foaming layers on top of the cokedue to the channels in the coke that cause higher localized velocity(vs. vapor flow of <1-2 fps above the foam layer designed fordisengagement of coke solids from the overhead vapors).

Catalyst can have characteristics of FCCU catalyst, hydroprocessingcatalyst (HPC), other catalysts, and any combination thereof to optimizereactions in liquid/emulsion and foaming layers to reduce the chemicalcompounds that would otherwise form coke.

If the degree of catalytic cracking is limited by the concentration ofhydrogen, the current Intellectual Property (IP) already contemplatesthe injection of hydrogen to the target reaction zone(s) by catalystimpregnation on the catalyst or otherwise. The IP also contemplatesother means of adding hydrogen to the reaction chemistry, including theaddition of hydrogen as an excess reactant in the form of a gas or achemical compound that releases hydrogen when heated or reacted withanother chemical compound.

Addition of Hydrogen to catalyst slurry may become desirable once youreach the equilibria limits due to hydrogen reactant concentration: Thiscan be in the form of hydrogen gas bubbled through slurry but morelikely impregnated on the catalyst to increase probability that hydrogenwill be available at the target reaction zone. This may be accomplishedby increasing the proton donor or electron receptor activity sites ofthe catalyst, catalyst impregnation, other methods, or any combinationthereof

Use of catalyst to promote exothermic reactions in the coke drum orelsewhere (e.g. heater or vapor line) is often desirable: CatalyticCoking: Polymerization coking, Other exothermic Coking Mechanisms;Catalytic Cracking: Promote exothermic cracking mechanisms.

If possible, the addition of catalyst to promote asphaltene coking withexothermic reactions (preferably after cracking off chains betweenaromatic plates of asphaltenes) would also increase the temperature ofthe coke drum, preferably at the liquids level to help promoteadditional desired cracking reactions of chemical compounds that wouldotherwise form coke

Catalysts promote the same reactions (cracking or coking) with less heatof reaction required: As a result, the heater outlet temperature isreduced less for the same reactions, and the coke drum vapor outlettemperature is increased, if this available heat is not consumed inadditional endothermic reactions. In addition, the temperature at theliquid/emulsion and foam layers would be increased, as well. This can beestimated by the evaluation of the change in the heats of reactions andthe quantity of catalyst used.

Said additive of the Technology may also be added in the vapor linebetween the coke drum and the fractionator (downstream of the cokedrum), but is typically not a preferred embodiment due to the potentiallower heat (less effective use of the catalyst) and the potentialproblems associated with catalyst (if used) or seeding agents (if used)getting into the fractionator or being recycled through the processheater. Also, the said additive could be introduced in the feed linebetween the heater and the coke drum (upstream of the coke drum), butwould likely encounter similar problems with catalyst being injected inthe feed prior to the process heater (i.e. catalyst and other materialsact as seeding agent that promotes more catalyst formation, not less)and would not be as effective use of the catalyst.

Said additive of the Technology may also be added by various mechanicalmeans to the foaming and/or liquid layers below the product vapors ofthe delayed coker. One means of accomplishing this is to use themodified drill stem discussed in previous patent filings. Thesemechanical means of injecting the said additive could be continuousinjection, intermittent or periodic injection, and/or batch injection(all at once per coking cycle). If the status of current technologies(e.g. high-pressure drum sealing technology, metallurgy of components,etc.) are not prohibitive at the current time, the use of the modifieddrum stem which can reliably follow the upward movement of the foamingand/or liquid layers throughout the coking cycle would provide apreferred embodiment to introduce active catalyst into the foamingand/or liquid layers.

Novel Use of Internal Recycle

As with the previous patent applications, the traditional delayed cokeroperation is modified by injecting an additive consisting of carrier oiland catalyst (with other options previously noted) into the coke drumabove the liquid layer. Though I believe these ideas have been discussedin previous patent applications and time stamped e-mails in some form oranother, I am submitting the following embodiments in the stated form tobe time stamped to assure clarity in their use in this manner:

-   -   1. Internal Recycle w/Various Options: In this embodiment, the        quench oil in the vapor line of a traditional delayed coking        operation downstream of the coke drum is decreased by the        equivalent amount of heat capacity (temperature reduction) as        the said additive injection. In this manner, the heat balance in        the coker is maintained. In addition, the components with the        highest boiling points in the product vapors that traditionally        exit the coke drum are condensed in the coke drum creating an        internal recycle (vs. becoming part of the external recycle that        goes through the coker fractionator and back to the inlet to the        coke charge heater and passing through the coke drum once more).        These product vapor components of highest boiling points are        preferentially condensed in a manner (e.g. catalyst as seeding        agent) that provides intimate contact with the catalyst for        increase selectivity of the desired reactions of these vapor        components. In this embodiment, the internal recycle allows        various process options and operational flexibility:        -   a. External recycle can be reduced and debottleneck the            coker charge heaters to allow more coker feed to be            processed, allowing more coker throughput. If the coker is            the refinery bottleneck, this may allow more refinery            throughput, as well.        -   b. If the external recycle is not reduced by the full amount            of said internal recycle (e.g. maintained at existing level            or a level in between), the heavy coker gas oil draw            temperature will be reduced accordingly. In this manner, the            heavy coker gas oil quality can be improved by reducing the            amount of ‘Heavy tail’ components in the heavy coker gas            oil. This quality improvement typically leads to more            efficient processing of the heavy coker gas oil in            downstream units (e.g. Less coke on catalyst in downstream            FCCU) or better characteristics for alternative uses (e.g.            better combustion characteristics for fuel).        -   c. Combination of benefits from partial or combination of a            and b above. For example, some of the internal recycle            amount is used for increased coker heater throughput with            associated increases in coker throughput and refinery            throughput (e.g. used to the extent that the coker heater is            no longer the bottleneck of the coker) and some of the            internal recycle amount is used for improvement of the heavy            coker gas oil quality.

Reducing the heater outlet temperature and various other means to reducethe overhead vapor line temperature may achieve similar benefits, withor without the use of the quench oil. In addition, these benefits(utility) may be sufficient to justify the implementation of thetechnology even without a reduction (or lower levels of reduction) inthe production of coke.

Injection of Additive Components in Separate Process Streams: In anotherembodiment, said additive components can be added to the coker productvapors in separate process streams. For example, the catalyst can beinjected separately from the carrier oil that acts as a quench oil toselectively condense the highest boiling components in the productvapors. The carrier oil in said additive may no longer carry otheradditive components, but simply become quench oil. This may bepreferable in applications (1) where the catalyst is more easilyinjected in a dry form and/or (2) where a catalyst of a highertemperature is desirable. In this example, the coincidental injection ofboth the quench oil and the catalyst near the same location may bedesirable in a manner that enhances the intimate contact of the catalystand condensed highest boiling point components of the coker productvapors to increase selectivity of the desired reactions. In anotherexample, hydrogen may be added as a separate process stream, as well.That is, the addition of hydrogen as a separate process stream may bepreferable, whether the remaining additive is injected in one processstream or multiple process streams.

In addition, a separate addition of colder catalyst may also bedesirable in certain applications. The colder catalyst may be sufficientto condense the highest boiling materials in the product gases toachieve a desired intimate contact with the coke (selective reactionwith catalyst), but the drop in temperature would not normally besufficient to condense a higher level of the highest boiling materialsdue to the lack of substantial heat loss from the heat of vaporizationin a carrier/quench oil.

Injection in the Vapor Line vs. Coke Drum w/Optional Catalyst collectionwith Coke Particles: In this embodiment, the injection of the saidadditive into the vapor line between coke drum and the cokerfractionator may be desirable in some applications of the technology.Though this embodiment would not have the benefit of higher temperaturesassociated with the reheat of the internal recycle (e.g. as thecatalyst/condensed coker product vapors sink to the liquid coking layerin the coke drum), some enhanced chemical reactions may still providesufficient benefits to justify its application. For example, saidadditive in the form of heated catalyst could be injected into the vaporline and achieve desired benefits. In this case, quench oil injection insaid vapor line may already exist in the coker of said application tocondense the highest boiling components of the coker product vapors. Inaddition, some applications may already have particulate collectiondevices near the inlet to the coker fractionator (e.g. before the cokerproduct vapors entrance to the coker fractionator) to collect cokeparticles. These existing particulate collection devices may besufficient to collect additional particulates from (1) solid componentsof said additive (e.g. catalyst) or (2) solid derivatives from reactionscaused by injection of said additive. Otherwise, the particulatecollection devices may be modified and/or new collection devices addedto handle the additional particulate loading and different particlecharacteristics.

Improvement of Coker Naphtha: In this embodiment, the said injection ofadditive may be used to improve the quality of the coker naphtha processstream. For example, the increased production of olefins caused by thepresence of the catalytic cracking can be optimized to produce naphthamore similar to naphtha process streams from other refinery processunits (e.g. Fluid catalytic Cracking Unit: FCCU). In this manner, thecoker naphtha stream in some applications may be treated similar toother naphtha process streams in the refinery, requiring less additionalprocessing and providing more value.

In another embodiment, the carrier oil and/or quench oil can beincreased to increase the quantity of highest boiling materials (e.g.recycle) that is condensed. In many cases, for each 1 wt. % of feed thatis injected into the top of the coke drum, roughly 10° F. drop in theproduct vapors temperature can be expected. In this example, 1 wt. %could be increased to 3 wt. % to achieve a 30° F. drop in the productvapor to increase the quantity of highest boiling materials condensed(e.g. recycle). This increase in carrier and/or quench oil can often bedone without any increase in cost or impact on the coker heat balance,since the quenching is simply moved forward (or transferred) from thevapor line to the top of the coke drum and the quench oil in either caseis recovered in the fractionator. In these cases, the catalystconcentration can also be varied to achieve the desired level ofinjection. For example, the catalyst concentration can be reduced by ⅓while raising the quench oil injection level by 3 to maintain the samelevel of total catalyst going into the coker system.

Differentiation Over Fluid Catalytic Cracking Process:

The known art of fluid catalytic cracking in the refining industry isvery different from the introduction of a catalytic additive in thecoking vessel of a coking process in exemplary embodiments of thepresent invention. The fluid catalytic cracking (FCC) process typicallyintroduces high boiling point hydrocarbon feed(s) into fluidizedcatalyst particles in a specially designed reactor (e.g. combinations offeed-riser and dense-bed reactors). The high boiling point feedstypically include heavy atmospheric gas oil, vacuum gas oil, and/orheavy coker gas oil (HCGO). The catalyst sufficiently lowers theactivation energy of cracking reactions to preferably promote thecatalytic cracking of these high boiling point materials to lowerboiling point hydrocarbon products, including gasoline and middledistillates. In addition, FCC catalysts typically increase some cokingreactions, as well. Thus, the FCC process also produces coke thatremains on the catalyst and rapidly lowers its activity. Consequently,the catalyst is circulated to a regeneration vessel, where the coke isburned off of the catalyst to regenerate catalyst activity to acceptablelevels.

The reaction conditions of the FCC reactor are also substantiallydifferent from the vapor zone of the coking vessel. The catalyticreactants in both processes typically include heavy coker gas oil, butthe vapor products in the coking vessel of the coking process alsoinclude higher boiling point compounds in the coker recycle componentand lower boiling point compounds in the components of light coker gasoil, naphtha, and gases. Typically, the FCC reactor pressure (e.g. 8-12psig) is slightly lower than the coking vessel (e.g. 12-25 psig). TheFCC reactor temperature (e.g. 900 to 1000 degrees Fahrenheit) issubstantially higher than the coking vessel (e.g. 800 to 900 degreesFahrenheit). Furthermore, the residence time of catalyst exposure to thereactants is substantially different: FCC typically measured in seconds,where the catalyst in the coking vessel can conceivably continue tocatalyze reactions for minutes to hours, depending on various factorsincluding fluidization in the coking vessel product vapors. Though theyboth have low partial pressures of hydrogen, the much higher residencetime and lower temperatures can favor substantially more cracking ofaromatic compounds in the coking vessel.

In conclusion, the catalytic cracking in the coking vessel in theexemplary embodiments of the present invention is substantiallydifferentiated over the known art of fluid catalytic cracking. Varioustypes of FCC catalyst (e.g. equilibrium, fresh, etc.) have been noted tobe a type of catalyst that has the desired characteristics for variousembodiments of the present invention. In this regard, the catalyticcracking and coking reactions of certain reactants (e.g. HCGO) areexpected to have similar characteristics. However, the basic reactordesign and reaction conditions are substantially different.

Utility of Exemplary Embodiments of the Present Invention:

Refinery computer optimization models can be used to establish theutility of various exemplary embodiments of the present invention. Mostrefineries currently use refinery optimization models (e.g. LP Models)to optimize refinery process operations to maximize profit (or otherobjectives), based on the refinery process scheme, refinery crude blend,and market values for final products. The optimization model typicallycontains individual models for each refinery process in its refineryprocess scheme to assess the optimal operation to best utilize itscapabilities and capacity. These refinery models typically estimatevalues of various process streams, including the feed and products of acoking process. In some models, the value of the ‘internal recycle’ insome exemplary embodiments of the present invention of a coking processcan be valued based on its effects on process capacity and associatedproducts. These values are typically generated in a dollars per barrelbasis (i.e. $/Bbl.), but can be readily converted to cents per pound(c/Lb.), as well. Typically, the relative rankings (lowest to highestvalue in c/Lb) of the coker process streams are as follows: coke(lowest), recycle, feed, refinery fuel gas, HCGO, LCGO, Naphtha, LPGs,and gaseous olefins (highest). The HCGO, LCGO, and naphtha values arecomparable and actually can have different relative rankings fromrefinery to refinery, due to differences in refinery process scheme andrefinery crude blend. For example, the FCC capacity and/or capacities ofdownstream processing units for LCGO and naphtha can have effects ontheir relative values. In refineries where the FCC capacity is limited,opportunities may exist to use an exemplary embodiment of the presentinvention to use the coking process as incremental capacity for crackingHCGO to LCGO, naphtha, and lighter components. In many refineries, therefinery fuel gas value is often over ten times higher in value than thecoke, and the other process streams are valued at 15 to 20 times higher.Consequently, most exemplary embodiments of the present invention thatcrack high boiling point materials that would otherwise form coke havevery high utility. An exception to this general rule exists inrefineries where coking small portions of HCGO or heavier material canimprove operations of coking process or downstream processes (e.g. FCCdue to better quality HCGO), and provide greater value. In addition, anexemplary embodiment of the present invention that cokes undesirablematerials in the HCGO can lead to improvement of coke quality andsufficiently leverage the coke value, while improving HCGO quality toreduce operating problems in downstream processing equipment (e.g. FCC).

In conclusion, the most favorable exemplary embodiment of the presentinvention will depend on its economic or upgrade value. In manyrefineries, the highest product upgrade value will be cracking thehighest boiling point materials that would otherwise form coke. Thus,exemplary embodiments of the present invention that produce less cokeand more liquids may provide the best upgrade value.

Description of an Example of Process Operation:

The operation of the equipment in FIG. 3 is straightforward, after theappropriate additive mixture has been determined. The components areadded to the heated (e.g. steam coils), mixing tank (or other means ofmixing and means of temperature regulation) with their respectivequality and quantity as determined in previous tests (e.g. commercialdemonstration). Whether the mixing is a batch or continuous basis, theinjection of the additive of this invention is injected into the cokingvessel while the coking process proceeds. In the semi-continuous processof the delayed coking, continuous injection is often preferable (but notrequired) in the drums that are in the coking cycle. However, in thesecases, injection at the beginning and end of the coking cycles may notbe preferable due to warm up and antifoam issues. Preferably, the flowrate of the additive of an example of the present invention will beproportional to the flow rate of the coker feed (e.g. 1.5 wt. %) and maybe adjusted accordingly as the feed flow rate changes.

In the general exemplary embodiment, the additive package is designedwith first priority given to selectively crack the high boiling pointcomponents in the coking vessel product vapors. Then, second priority isgiven to selectively coke the remaining high boiling point components.In other words, the additive will condense and selectively remove thesehigh boiling point components from the product vapors and help themeither crack or coke, with preference given to cracking versus coking.This is primarily achieved by the choice of catalyst. For example,residua cracking catalysts that are traditionally used for cracking incatalytic cracking units (e.g. Fluid Catalytic Cracking Unit or FCCU)may be very effective in this application to crack the heavy aromaticsmolecules into lighter ‘cracked liquids’. These catalysts have a higherdegree of mesoporosity and other characteristics that allow the largemolecules of the high boiling point components to have better access toand from the catalyst's active cracking sites. In addition, the othercomponents of the additive package may influence cracking reactions overcoking reactions, as well. As described previously, it is anticipatedthat various catalysts will be designed for the purposes above,particularly catalysts to achieve greater cracking of the highestboiling point materials in the coking process product vapors. In manycases, conversion of the highest boiling point product vapors to cokemay predominate (e.g. >70 Wt. %) due to their higher propensity to coke(vs. crack). However, with certain chemical characteristics of thesematerials, properly designed catalysts, and the proper coker operatingconditions, substantial conversion of these materials to cracked liquidsmay be accomplished (e.g. >50 Wt. %). Conceivably, cracking of heavyhydrocarbons (that would otherwise become coke, recycle material, or‘heavy tail’ of the heavy coker gas oil) could be sufficient to reduceoverall coke production, reduce coker recycle, and/or reduce heavy gasoil production, particularly the ‘heavy tail’ components.

In many cases, the achievement of additional cracking of these highestboiling point materials in the product vapors to ‘cracked liquids’products is worth the cost of fresh cracking catalyst versus spent orregenerated catalyst. This economic determination will depend on thechemical structures of the high boiling point components. That is, manyof the highest boiling point components often have a high propensity tocoke and will coke rather than crack, regardless of the additive packagedesign. If sufficient high boiling point components are of this type,the economic choice of catalyst may include spent, catalyst(s),regenerated catalyst(s), fresh catalyst(s), or any combination thereof.In a similar manner, cracking catalysts, in general, may not bedesirable in cases where almost all of the highest boiling pointcomponents have very high propensities to coke, and inevitably becomecoke, regardless of the additive package design.

In its preferred embodiment, this additive selectively cracks the heavycoker gas oil's heaviest aromatics that have the highest propensity tocoke, while quenching cracking reactions in the vapor, facilitatingcracking reactions in the condensed vapors, and/or provides antifoamingprotection.

Working Examples of General Exemplary Embodiments:

In order to more thoroughly describe the present invention, thefollowing working examples are presented. The data presented in theseexamples was obtained in a pilot-scale, batch coker system. The primarycomponent of this pilot-scale coker system is a stainless steelcylindrical reactor with an internal diameter of 3.0 inches and a heightof 39 inches. A progressive cavity pump transfers the coker feed fromthe heated feed tank with mixer to the preheater and coker reactor. Thenominal feed charge for each test is 4000 to 5000 grams over a 4-5 hourperiod. The preheater and coker temperatures are electronicallycontrolled in an insulated furnace to the desired set points. A backpressure controller is used to maintain the desired reactor pressure.This pilot-scale system was used to generate data to demonstrate thebenefits of the current invention over the known art. That is, theinjection of the catalyst additive into the coking vessel of the currentinvention and the addition of catalyst to the coker feed of the knownart were compared to a common baseline with no catalyst.

Comparative Test Examples 1 and 2

Coker feed from a commercial refinery was used to generate data for twotests with equivalent amounts of catalyst B. The operating conditionsand the test results are shown in the following table.

Run Number 94 100 vs.94 CT-1 vs.94 vs.100 100% 100% Valero Vac ValeroValero Resid + Vac Vac CatB + Feed Blend Units Resid Resid AntiFoam TestConditions Average Drum Pressure psig 18.4 19.6 19.5 Average DrumTemperatures Coke drum inlet temp ° C. 483 485 487 Coke drumlower/middle temp ° C. 463 456 457 Coke drum top temp ° C. 421 430 427Material Fed to Reactor grams 4814 5000 4543 Time for Test minutes 290270 Average Feed Rate g/min 17.2 16.8 Injected Injected Cat in at Top atTop Feed Decanted Slurry Oil w/Anti-Foam grams 160 180 3.6% CatalystSystem NA B B No Cat Catalyst Quantity (Wt. % of Slurry) grams 0.0 24.113.4% Slurry Catalyst Quantity (Wt. % of Feed) grams 0.0 24.1 0.5% 21.90.5% Test Results Material Fed to Reactor grams 4814 5000 4543 ProductsCoke grams 1613 1584 1672 Liquid grams 2557 2783 2323 Gas (bydifference) grams 644 633 548 Product Yields Coke Wt. % 33.5% 31.7%−5.5% 36.8% 9.8% 16.2% Liquid Wt. % 53.1% 55.7% 4.8% 51.1% −3.7% −8.1%Gas Wt. % 13.4% 12.7% −5.4% 12.1% −9.9% −4.8%

In the foregoing table, the catalyst addition of the known art showed asubstantial increase in coking and a significant reduction in liquidyields. In contrast, the injection of the catalytic additive of thepresent invention showed a substantial reduction in coke yield and asignificant increase in liquids production. Thus, these tests clearlydemonstrate differentiation of the present invention over the known art.As described above, these results are likely due to the majordifferences in the chemical and physical nature of the primaryreactants, exposed to the catalyst.

Comparative Test Examples 2, 3, and 4

Similarly, the coker feed from the same commercial refinery was used togenerate data for 3 tests with equivalent amounts of catalyst C. Theoperating conditions and the test results are shown in the followingtable.

Run Number 94 108 vs.94 CT-2 vs.94 vs.108 CT-3 vs.94 vs.108 100% 100%Valero Valero Vac Valero Valero Vac Resid + Resid + Vac Vac CatC +CatC + Feed Blend Units Resid Resid AntiFoam Anti Foam Test ConditionsAverage Drum Pressure psig 18.4 17.4 17.5 17.5 Average Drum TemperaturesCoke drum inlet temp ° C. 483 480 476 477 Coke drum lower/middle temp °C. 463 455 455 455 Coke drum top temp ° C. 421 429 431 432 Material Fedto Reactor grams 4814 4062 3952 3715 Time for Test minutes 279 281 263Average Feed Rate g/min 14.6 14.1 14.1 Injected Injected Cat in Cat inat Top at Top Feed Feed Decanted Slurry Oil w/Anti-Foam grams 160 1393.4% Catalyst System NA C C C No Cat No Cat Catalyst Quantity (Wt. % ofSlurry) grams 0.0 19.3 13.9% Slurry Slurry Catalyst Quantity (Wt. % ofFeed) grams 0.0 19.3 0.5% 18.8 0.5% 17.7 0.5% Test Results Material Fedto Reactor grams 4814 4062 3952 3715 Products Coke grams 1613 1309 13681279 Liquid grams 2557 2273 2009 1896 Gas (by difference) grams 644 480575 540 Product Yields Coke Wt. % 33.5% 32.2% −3.8% 34.62% 3.3% 7.4%34.43% 2.7% 6.9% Liquid Wt. % 53.1% 56.0% 5.4% 50.84% −4.3% −9.2% 51.04%−3.9% −8.8% Gas Wt. % 13.4% 11.8% −11.7% 14.55% 8.7% 23.1% 14.54% 8.6%23.0%

In the foregoing table, the catalyst addition of the known art showed asubstantial increase in coking and a significant reduction in liquidyields. In contrast, the injection of the catalytic additive of thepresent invention showed a substantial reduction in coke yield and asignificant increase in liquids production. Thus, these tests clearlydemonstrate differentiation of the present invention over the known art.As described above, these results are likely due to the majordifferences in the chemical and physical nature of the primaryreactants, exposed to the catalyst.

Description and Operation of Alternative Exemplary Embodiments DelayedCoking Process

There are various ways exemplary embodiments of the present inventionmay improve the delayed coking process. A detailed description of howthe invention is integrated into the delayed coking process is followedby discussions of its operation in the delayed coking process andalternative exemplary embodiments relative to its use in this commontype of coking process.

Traditional Delayed Coking Integrated with Exemplary Embodiments of thePresent Invention

FIG. 2 is a basic process flow diagram for the traditional delayedcoking process of the known art. Delayed coking is a semi-continuousprocess with parallel coking drums that alternate between coking anddecoking cycles. Exemplary embodiments of the present inventionintegrate an additive addition system into the delayed coking processequipment. The operation with an example of the present invention issimilar, as discussed below, but significantly different.

In general, delayed coking is an endothermic reaction with the furnacesupplying the necessary heat to complete the coking reaction in the cokedrum. The exact mechanism of delayed coking is so complex that it is notpossible to determine all the various chemical reactions that occur, butthree distinct steps take place:

1. Partial vaporization and mild cracking of the feed as it passesthrough the furnace2. Cracking of the vapor as it passes through the coke drum3. Successive cracking and polymerization of the heavy liquid trapped inthe drum until it is converted to vapor and coke.

In the coking cycle, coker feedstock is heated and transferred to thecoke drum until full. Hot residua feed 10 (most often the vacuum towerbottoms) is introduced into the bottom of a coker fractionator 12, whereit combines with condensed recycle. This mixture 14 is pumped through acoker heater 16, where the desired coking temperature (normally between900 degrees F. and 950 degrees F.) is achieved, causing partialvaporization and mild cracking. Steam or boiler feed water 18 is ofteninjected into the heater tubes to prevent the coking of feed in thefurnace. Typically, the heater outlet temperature is controlled by atemperature gauge 20 that sends a signal to a control valve 22 toregulate the amount of fuel 24 to the heater. A vapor-liquid mixture 26exits the heater, and a control valve 27 diverts it to a coking drum 28.Sufficient residence time is provided in the coking drum to allowthermal cracking and coking reactions to proceed to completion. Bydesign, the coking reactions are “delayed” until the heater chargereaches the coke drums. In this manner, the vapor-liquid mixture isthermally cracked in the drum to produce lighter hydrocarbons, whichvaporize and exit the coke drum. The drum vapor line temperature 29(i.e., temperature of the vapors leaving the coke drum) is the measuredparameter used to represent the average drum outlet temperature.Petroleum coke and some residuals (e.g. cracked hydrocarbons) remain inthe coke drum. When the coking drum is sufficiently full of coke, thecoking cycle ends. The heater outlet charge is then switched from thefirst coke drum to a parallel coke drum to initiate its coking cycle.Meanwhile, the decoking cycle begins in the first coke drum. Lighterhydrocarbons 38 are vaporized, removed overhead from the coking drums,and transferred to a coker fractionator 12, where they are separated andrecovered. Coker heavy gas oil (HGO) 40 and coker light gas oil (LGO) 42are drawn off the fractionator at the desired boiling temperatureranges: HGO: roughly 610-800 degrees F.; LGO: roughly 400-610 degrees F.The fractionator overhead stream, coker wet gas 44, goes to a separator46, where it is separated into dry gas 48, water 50, and unstablenaphtha 52. A reflux fraction 54 is often returned to the fractionator.

In the decoking cycle, the contents of the coking drum are cooled down,remaining volatile hydrocarbons are removed, the coke is drilled fromthe drum, and the coking drum is prepared for the next coking cycle.Cooling the coke normally occurs in three distinct stages. In the firststage, the coke is cooled and stripped by steam or other stripping media30 to economically maximize the removal of recoverable hydrocarbonsentrained or otherwise remaining in the coke. In the second stage ofcooling, water or other cooling media 32 is injected to reduce the drumtemperature while avoiding thermal shock to the coke drum. Vaporizedwater from this cooling media farther promotes the removal of additionalvaporizable hydrocarbons. In the final cooling stage, the drum isquenched by water or other quenching media 34 to rapidly lower the drumtemperatures to conditions favorable for safe coke removal. After thequenching is complete, the bottom and top heads of the drum are removed.The petroleum coke 36 is then cut, typically by a hydraulic water jet,and removed from the drum. After coke removal, the drumheads arereplaced, the drum is preheated, and otherwise readied for the nextcoking cycle.

Exemplary embodiments of the present invention may be readily integratedinto the traditional, delayed coker system, both new and existing. Asshown in FIG. 3, this process flow diagram shows the traditional delayedcoking system of FIG. 2 with the addition of an example of the presentinvention. This simplified example shows the addition of a heated,mixing tank (210) (an exemplary means of mixing and a means oftemperature regulation) where components of the present invention'sadditive may be blended: catalyst(s) (220), seeding agent(s) (222),excess reactant(s) (224), carrier fluid(s) (226), and/or quenchingagent(s) (228). The mixed additive (230) is then injected into the uppercoke drums (28) above the vapor/liquid interface of the delayed cokingprocess via properly sized pump(s) (250) (an exemplary means ofpressurized injection) and piping, preferably with properly sizedatomizing injection nozzle(s) (260). In this case, the pump iscontrolled by a flow meter (270) with a feedback control system relativeto the specified set point for additive flow rate.

Process Control of Traditional Delayed Coking with Exemplary Embodimentsof the Present Invention

In traditional delayed coking, the optimal coker operating conditionshave evolved through the years, based on much experience and a betterunderstanding of the delayed coking process. Operating conditions havenormally been set to maximize (or increase) the efficiency of feedstockconversion to cracked liquid products, including light and heavy cokergas oils. More recently, however, the cokers in some refineries havebeen changed to maximize (or increase) coker throughput.

In general, the target operating conditions in a traditional delayedcoker depend on the composition of the coker feedstocks, other refineryoperations, and coker design. Relative to other refinery processes, thedelayed coker operating conditions are heavily dependent on thefeedstock blends, which vary greatly among refineries (due to varyingcrude blends and processing scenarios). The desired coker products andtheir required specifications also depend greatly on other processoperations in the particular refinery. That is, downstream processing ofthe coker liquid products typically upgrades them to transportation fuelcomponents. The target operating conditions are normally established bylinear programming (LP) models that optimize the particular refinery'soperations. These LP models typically use empirical data generated by aseries of coker pilot plant studies. In turn, each pilot plant study isdesigned to simulate the particular refinery's coker design. Appropriateoperating conditions are determined for a particular feedstock blend andparticular product specifications set by the downstream processingrequirements. The series of pilot plant studies are typically designedto produce empirical data for operating conditions with variations infeedstock blends and liquid product specification requirements.Consequently, the coker designs and target operating conditions varysignificantly among refineries.

In common operational modes, various operational variables are monitoredand controlled to achieve the desired delayed coker operation. Theprimary independent variables are feed quality, heater outlettemperature, coke drum pressure, and fractionator hat temperature. Theprimary dependent variables are the recycle ratio, the coking cycle timeand the drum vapor line temperature. The following target control rangesare normally maintained during the coking cycle for these primaryoperating conditions:

1. Heater outlet temperatures in range of about 900 to about 950 degreesFahrenheit,2. Coke drum pressure in the range of about 15 psig to 100 psig:typically 20-30 psig,3. Hat Temperature: Temperature of vapors rising to gas oil drawoff trayin fractionator4. Recycle Ratio in the range of 0-100%; typically 10-20%5. Coking cycle time in the range of about 12 to 24 hours; typically15-20 hours6. Drum Vapor Line Temperature 50 to 100 degrees Fahrenheit less thanthe heater outlet temperature: typically 850-900 degrees Fahrenheit.

These traditional operating variables have primarily been used tocontrol the quality of the cracked liquids and various yields ofproducts. Throughout this discussion, “cracked liquids” refers tohydrocarbon products of the coking process that have 5 or more carbonatoms. They typically have boiling ranges between 97 and 870 degreesFahrenheit, and are liquids at standard conditions. Most of thesehydrocarbon products are valuable transportation fuel blendingcomponents or feedstocks for further refinery processing. Consequently,cracked liquids may be a primary objective of a coking process.

Over the past ten years, some refineries have switched coker operatingconditions to maximize (or increase) the coker throughput, instead ofmaximum efficiency of feedstock conversion to cracked liquids. Due toprocessing heavier crude blends, refineries often reach a limit incoking throughput that limits (or bottlenecks) the refinery throughput.In order to eliminate this bottleneck, refiners often change the cokeroperating conditions to maximize (or increase) coker throughput in oneof three ways:

1. If coker is fractionator (or vapor) limited, increase drum pressure(e.g. 15 to 20 psig.)2. If coker is drum (or coke make) limited, reduce coking cycle time(e.g. 16 to 12 hours)3. If Coker is heater (or feed) limited, reduce recycle (e.g. 15 wt. %to 12 wt. %) All three of these operational changes increase the cokerthroughput. Though the first two types of higher throughput operationreduce the efficiency of feedstock conversion to cracked liquids (i.e.,per barrel of feed basis), they may maximize (or increase) the overallquantity (i.e., barrels) of cracked liquids produced. These operationalchanges also tend to increase coke yield and coke VCM. However, anyincrease in drum pressure or decrease in coker cycle time is usuallyaccompanied by a commensurate increase in heater outlet and drum vaporline temperatures to offset (or limit) any increases in coke yield orVCM. In contrast, the reduction in recycle is often accomplished by areduction in coke drum pressure and an increase in the heavy gas oil endpoint (i.e., highest boiling point of gas oil). The gas oil end point iscontrolled by refluxing the trays between the gas oil drawoff and thefeed tray in the fractionator with partially cooled gas oil. Thisoperational mode increases the total liquids and maintains theefficiency of feedstock conversion to cracked liquids (i.e., per barrelof feed basis). However, the increase in liquids is primarily highestboiling point components (i.e., ‘heavy tail’) that are undesirable indownstream process units. In this manner, ones skilled in the art ofdelayed coking may adjust operation to essentially transfer thesehighest boiling point components to either the recycle (which reducescoker throughput) or the ‘heavy tail’ of the heavy gas oil (whichdecreases downstream cracking efficiency). An exemplary embodiment ofthe present invention provides the opportunity to (1) increase cokerthroughput (regardless of the coker section that is limiting), (2)increase liquid yields, and (3) may substantially reduce highest boilingpoint components in either recycle, heavy gas oil, or both. In thismanner, each application of an exemplary embodiment of the presentinvention may determine which process is preferable to reduce theundesirable, highest boiling point components.

Impact of Exemplary Embodiments of Present Invention on Delayed CokingProcess

There are various ways examples of the present invention may improveexisting or new delayed coking processes in crude oil refineries andupgrading systems for synthetic crudes. These novel improvementsinclude, but should not be limited to, (1) catalytic cracking of heavyhydrocarbons that would otherwise become pet coke, recycle, or heavytail′ components of the heavy gas oil, (2) catalytic coking of heavyaromatics in a manner that promotes sponge coke morphology and reduces‘hotspots’ in coke cutting, (3) quenching drum outlet gases that reduce‘vapor overcracking’, (4) debottlenecking all major sections of thedelayed coking process (i.e., heater, drum, & fractionator sections, and(5) reducing recycle and vapor loading of fractionator.

In all the examples for delayed coking processes, an exemplaryembodiment of the present invention may achieve one or more of thefollowing: (1) improved coker gas oil quality, (2) improved coke qualityand market value, (3) less gas production, (4) less coke production, (5)increased coker and refinery capacities, (6) increased use of cheaper,lower quality crudes and/or coker feeds, (7) increased efficiency andrun time of downstream cracking units, (8) decreased operation &maintenance cost of coker and downstream cracking units, and (9) reducedincidents of ‘hotspots’ in pet coke drum cutting, and (10) reducedcatalyst make-up and emissions in downstream cracking units.

Example 1

In fuel grade coke applications, the delayed coking feedstocks are oftenresiduals derived from heavy, sour crude, which contain higher levels ofsulfur and metals. As such, the sulfur and metals (e.g. vanadium andnickel) are concentrated in the pet coke, making it usable only in thefuel markets. Typically, the heavier, sour crudes tend to cause higherasphaltene content in the coking process feed. Consequently, theundesirable ‘heavy tail’ components (e.g. PAHs) are more prominent andpresent greater problems in downstream catalytic units (e.g. cracking).In addition, the higher asphaltene content (e.g. >15 wt. %) often causesa shot coke crystalline structure, which may cause coke cutting ‘hotspots’ and difficulties in fuel pulverization.

In these systems, an example of the present invention provides theselective cracking and coking of the ‘heavy tail’ components (e.g. Heavyhydrocarbons) in coker gas oil of the traditional delayed cokingprocess. Typically, gas oil end points are selectively reduced from over950 degrees of Fahrenheit to 900 degrees of Fahrenheit or less (e.g.preferably <850 degrees of Fahrenheit in some cases). With greateramounts of additive, additional heavy components of the heavy coker gasoil and the coker recycle will be selectively cracked or coked. Thisimproves coker gas oil quality/value and the performance of downstreamcracking operations. In addition, the selective cracking of Heavyhydrocarbons and quench (thermal & chemical) of the vapor overcrackingimproves the value of the product yields and increases the ‘crackedliquids’ yields. Also, the reduction of heavy components that have ahigh propensity to coke reduces the buildup of coke in the vapor linesand allows the reduction of recycle and heater coking.

With a properly designed additive package (e.g. catalyst & excessreactants), an example of the present invention may also be effectivelyused to alleviate problems with ‘hot spots’ in the coke drums oftraditional delayed coking. That is, the heavy liquids that remain inthe pet coke and cause the ‘hot spots’ during the decoking cycle (e.g.coke cutting) are encouraged to further crack (preferable) or coke bythe catalyst and excess reactants in the additive package. To this end,catalyst(s) and excess reactant(s) for this purpose may include, butshould not be limited to, FCCU catalysts, hydrocracker catalysts,activated carbon, crushed coke, FCCU slurry oil, and coker heavy gasoil.

In fuel grade applications, the choice of catalyst(s) in the additivepackage has greater number of options, since the composition of thecatalyst (e.g. metals) is less of an issue in fuel grade pet cokespecifications (e.g. vs. anode). Thus, the catalyst may containsubstrates and exotic metals to preferentially and selectively crack(vs. coke) the undesirable, heavy hydrocarbons (e.g. PAHs). Again,catalyst(s) and excess reactant(s) for this purpose may include, butshould not be limited to, FCCU catalysts, hydrocracker catalysts, iron,activated carbon, crushed coke, FCCU slurry oil, and coker heavy gasoil. The most cost effective catalyst(s) may include spent orregenerated catalysts from downstream units (e.g. FCCU, hydrocracker,and hydrotreater) that have been sized and injected in a manner toprevent entrainment in coking process product vapors to thefractionator. In fact, the nickel content of hydrocracker catalyst maybe very effective in selectively coking the undesirable, heavycomponents (e.g. PAHs) of coker gas oil. The following example is givento illustrate a cost effective source of catalyst for an exemplaryembodiment of the present invention. A certain quantity of FCCUequilibrium catalyst of the FCCU is normally disposed of on a regularbasis (e.g. daily) and replaced with fresh FCCU catalyst to keepactivity levels up. The equilibrium catalyst is often regenerated priorto disposal and could be used in an exemplary embodiment of the presentinvention to crack the heavy hydrocarbons, particularly if the FCCUcatalyst is designed to handle residua in the FCCU feed. If theequilibrium catalyst does not provide sufficient cracking catalystactivity, it could be blended with a new catalyst (e.g. catalystenhancer) to achieve the desired activity while maintaining acceptablecatalyst costs.

When applied to greater degrees, an example of the present invention mayalso be used to improve the coke quality while improving the value ofcoke product yields and improved operations and maintenance of the cokerand downstream units. That is, continually increasing the additivepackage will incrementally crack or coke the heaviest remaining vapors.The coking of these components will tend to push coke morphology towardsponge coke and increased VCM. In addition, with the proper additivepackage the additional VCM will be preferentially greater than 950degrees Fahrenheit theoretical boiling point.

Example 2

In anode grade coke applications, examples of the present invention mayprovide substantial utility for various types of anode grade facilities:(1) refineries that currently produce anode coke, but want to addopportunity crudes to their crude blends to reduce crude costs and (2)refineries that produce pet coke with sufficiently low sulfur andmetals, but shot coke content is too high for anode coke specifications.In both cases, examples of the present invention may be used to reduceshot coke content to acceptable levels, even with the presence ofsignificant asphaltenes (e.g. >15 wt. %) in the coker feed.

With an exemplary embodiment of the present invention, refineries thatcurrently produce anode quality coke may often add significant levels ofheavy, sour opportunity crudes (e.g. >5 wt. %) without causing shot cokecontent higher than anode coke specifications. That is, an exemplaryembodiment of the present invention converts the highest boiling pointmaterials in the product vapors in a manner that preferably producessponge coke crystalline structure (coke morphology) rather than shotcoke crystalline structure. Thus, these refineries may reduce crudecosts without sacrificing anode quality coke and its associated highervalues.

With an exemplary embodiment of the present invention, refineries thatcurrently produce shot coke content above anode coke specifications mayreduce shot coke content to acceptable levels in many cases. That is, anexemplary embodiment of the present invention converts the highestboiling point materials in the product vapors in a manner thatpreferably produces sponge coke crystalline structure (coke morphology)rather than shot coke crystalline structure. Thus, these refineries mayincrease the value of its petroleum coke while maintaining or improvingcoker product yields and coker operation and maintenance.

In both anode coke cases, the additive package must be designed tominimize any increases in the coke concentrations with respect tosulfur, nitrogen, and metals that would add impurities to the aluminumproduction process. Thus, the selection of catalyst(s) for these caseswould likely include alumina or carbon based (e.g. activated carbon orcrushed coke) catalyst substrates.

In both anode coke cases, the additive package must be designed tominimize the increase in VCMs and/or preferably produces additional VCMswith theoretical boiling points greater than 1250 degrees Fahrenheit.Thus, catalyst(s) and excess reactants for this additive package wouldbe selected to promote the production of sponge coke with highermolecular weights caused by significant polymerization of the highestboiling point materials in the product vapors and the excess reactants.In these cases, an optimal level of VCMs greater than 1250 degreesFahrenheit may be desirable to (1) provide volatilization downstream ofthe upheat zone in the coke calciner and (2) cause recoking of thesevolatile materials in the internal pores of the calcined coke. Theresulting calcined coke will preferably have a substantially greatervibrated bulk density and require less pitch binder to be adsorbed inthe coke pores to produce acceptable anodes for aluminum productionfacilities. In this manner, a superior anode coke may be produced thatlowers anode production costs and improves their quality. Beyond thisoptimal level of VCMs greater than 1250 degrees Fahrenheit, any cokeproduced by an exemplary embodiment of the present invention willpreferably not contain any VCMs. That is, any further coke produced willall have theoretical boiling points greater than 1780 degreesFahrenheit, as determined by the ASTM test method for VCMs.

Example 3

In needle coke applications, the coking process uses special coker feedsthat preferably have high aromatic content, but very low asphaltenecontent. These types of coker feeds are necessary to achieve the desiredneedle coke crystalline structure. These delayed coker operations havehigher than normal heater outlet temperatures and recycle rates. With anexemplary embodiment of the present invention, these coking processesmay maintain needle coke crystalline structure with higherconcentrations of asphaltenes and lower concentrations of aromatics inthe coker feed. Also, an exemplary embodiment of the present inventionmay reduce the recycle rate required to produce the needle cokecrystalline structure, potentially increasing the coker capacity andimproving coker operations and maintenance. In this manner, an exemplaryembodiment of the present invention may decrease coker feed costs, whilepotentially increasing needle coke production and profitability.

Example 4

Some delayed coker systems have the potential to produce petroleum cokefor certain specialty carbon products, but do not due to economic and/orsafety concerns. These specialty carbon products include (but should notbe limited to) graphite products, electrodes, and steel productionadditives. An exemplary embodiment of the present invention allowsimproving the coke quality for these applications, while addressingsafety concerns and improving economic viability. For example, certaingraphite product production processes require a petroleum coke feed thathas higher VCM content and preferably sponge coke crystalline structure.An exemplary embodiment of the present invention may be optimized tosafely and economically produce the pet coke meeting the uniquespecifications for these applications. Furthermore, the quality of theVCMs may be adjusted to optimize the graphite production process and/ordecrease process input costs.

CONCLUSION, RAMIFICATIONS, AND SCOPE OF THE INVENTION

Thus the reader will see that the coking process modification of theinvention provides a highly reliable means to catalytically crack orcoke the high boiling point components (e.g. heavy hydrocarbons) in theproduct vapors in the coking vessel. This novel coking processmodification provides the following advantages over traditional cokingprocesses and recent improvements: (1) improved coker gas oil quality,(2) improved coke quality and market value, (3) less gas production, (4)less coke production, (5) increased coker and refinery capacities, (6)increased use of cheaper, lower quality crudes and/or coker feeds, (7)increased efficiency and run time of downstream cracking units, (8)decreased operation & maintenance cost of coker and downstream crackingunits, and (10) reduced catalyst make-up and emissions in downstreamcracking units.

While my above description contains many specificities, these should notbe construed as limitations on the scope of the invention, but rather asan exemplification of embodiments thereof. Many other variations arepossible.

Any embodiment of the present invention may include any of the optionalor preferred features of the other embodiments of the present invention.The exemplary embodiments herein disclosed are not intended to beexhaustive or to unnecessarily limit the scope of the invention. Theexemplary embodiments were chosen and described in order to explain theprinciples of the present invention so that others skilled in the artmay practice the invention. Having shown and described exemplaryembodiments of the present invention, those skilled in the art willrealize that many variations and modifications may be made to thedescribed invention. Many of those variations and modifications willprovide the same result and fall within the spirit of the claimedinvention. Accordingly, the scope of the invention should be determinednot by the embodiment(s) illustrated, but by the claims and their legalequivalents.

What is claimed is:
 1. A process comprising introducing: an additivecomprising catalyst(s) alone or in combination with seeding agent(s),excess reactant(s), quenching agent(s), carrier fluid(s), or anycombination thereof into a coking vessel of a delayed coking processduring a coking cycle; and excess reactant(s) containing hydrogen into acoker feed, into a transfer line between a coker heater and a coke drum,into the coking vessel of the delayed coking process, or any combinationthereof; wherein said excess reactant(s) promote cracking of heavyhydrocarbons.
 2. A process of claim 1 wherein said excess reactant(s)containing hydrogen comprise gaseous hydrogen, chemical compounds thatrelease reactive hydrogen at higher temperatures, Lewis Acids, BronsteadAcids, or any combination thereof.
 3. A process of claim 2 wherein saidreactant(s) containing hydrogen provide a 0.5:1 to 3:1 molar ratio ofreactive hydrogen to coker feed.
 4. A process of claim 2 wherein saidreactant(s) containing hydrogen provide hydrogen to the targetedreaction zones at a rate of 30 to 600 Standard Cubic Feet per barrel ofcoker feed.
 5. A process of claim 1 wherein said reactant(s) containinghydrogen promote catalytic cracking, thermal cracking, or anycombination thereof.
 6. A process of claim 1 wherein said additive isadded to vapors above a vapor-liquid interface in said coking vessel. 7.A process of claim 1 wherein said additive is added to said cokingprocess by pressurized injection.
 8. A process of claim 1 whereincomponents of said additive are combined by mixing that provides asufficient level of blending said components prior to addition to saidcoking vessel of said coking process.
 9. A process of claim 1 wherein atemperature of said additive is regulated by temperature control thatprovides a predetermined temperature level of said additive mixtureprior to addition to said coking vessel of said coking process.
 10. Aprocess of claim 1 wherein said catalyst lowers an energy required forcracking reactions, coking reactions, or any combination thereof.
 11. Aprocess of claim 1 wherein said catalyst is a catalyst that providespropagation of carbon based free radicals that facilitate cracking andcoking reactions.
 12. A process of claim 1 wherein said catalystcomprises alumina, silica, zeolite, calcium, activated carbon, crushedpet coke, or any combination thereof.
 13. A process of claim 1 whereinsaid catalyst comprises new catalyst, FCCU equilibrium catalyst, spentcatalyst, regenerated catalyst, pulverized catalyst, classifiedcatalyst, impregnated catalysts, treated catalysts, or any combinationthereof.
 14. A process of claim 1, wherein said catalyst has particlesize characteristics to prevent entrainment in vapors, to achievefluidization in the coking vessel and increase residence time in saidvapors, or any combination thereof.
 15. A process of claim 1 furthercomprising cracking of heavy hydrocarbons in said coking vessel tolighter hydrocarbons that leave the coking vessel as vapors and enter adownstream fractionator where said lighter hydrocarbons are separatedinto process streams that are useful in oil refinery product blending.16. A process of claim 15 wherein said lighter hydrocarbon streamscomprise naphtha, gas oil, gasoline, kerosene, jet fuel, diesel fuel,heating oil, or any combination thereof.
 17. A process comprisingintroducing: an additive by pressurized injection into a coking vesselof a delayed coking process during a coking cycle to promote cracking ofheavy hydrocarbons, wherein said additive comprises crackingcatalyst(s), alone or in combination with seeding agent(s), excessreactant(s), quenching agent(s), carrier fluid(s), or any combinationthereof; and excess reactant(s) containing hydrogen into a coker feed,into a transfer line between a coker heater and a coke drum, into acoking vessel of a delayed coking process, or any combination thereof;wherein said hydrogen from said excess reactant(s) promote cracking ofheavy hydrocarbons.